At the core of dungeon crawlers, once the fantasy veneer is stripped away, is resource management. While overly obvious and reductive statements like this aren't really interesting, I think it's important to underline some concepts here. Let's talk about resources.
Light
Light is probably the most common "resource" that is associated with dungeon crawlers, and also very critical. It is easy to imagine that loss of light and all light-granting resources would just mean a TPK situation. Light is also very hard to reduce. You could imagine going on half rations for food to let them last a bit longer, but you can't really burn half a torch for less light- many games don't even have partial or low-light rules beyond other "you can see" or "you can't see". Light is also a very off or on resource in the fact that many fantasy races don't need light to see in darkness- comparatively few mechanics have in-universe methods of granting permanent, unlimited access to it. Comparatively few fantasy races have the ability of things like; don't need food or don't need arrows to shoot a bow or don't need to conserve hit points, etc.
The concept of light as a resource is often broken down into what the players can bring- namely Torches, Oil, and spells. Stranger forms of light resources- such as a racial ability to create light once p. day or a friendly torchbug companion that can glow to light up a room for you and so on go beyond the scope of this list.
Torches could be thought of as anything burnable. Potentially anything long and straight could be made as a torch or primitive torch. Real torches (as real candles) have specific methods of production; you can't just burn the end of a branch to make an effective torch. But this is fantasyland and it will work in a pinch.
Oil is more complex. Is it whale oil, plant oil, or magical fantasy oil? The concept to restore oil out of the bodies of slain monsters is a good one. Also; burning oil could make different smells- so a tribe of hobgoblins wouldn't notice your whale-oil-lamp but when they smell their chieftan burning to light your lantern then they'll get pissed. Oil is also in my opinion one of the most likely things you'll actually find in a traditional dungeon; any mineshaft or deep underground cave could have an oil drum or barrel left by the excavators or previous adventuring groups.
Light making spells is magic, and as such little rules of reality apply. Anything that can restore magic, or power from a patron of light/holy magic, or connection to the surface world for a druid, etc. could be used to restore light from a light spell. Another idea; a magical/holy light spell that gets dimmer the longer it goes on, but can be refreshed by brutal blood sacrifice of sentient beings. Imagine sacrificing bat people to Quetzalcoatl so you can search for more of that Aztec gold.
Rations & Feed
Food is the easiest thing to resupply in the dungeon; just eat monsters. Mushrooms are also around. Dungeon Meshi ran with this entire concept; it's good.
Feeding animals, especially herbivores (cave donkey?) is a bit harder and would require some supernatural elements. I like the Dwarf Fortress method of cave moss being good enough for surface dwelling herbivores to consume and survive on. In some parts of subterranian caverns it grows like a thick blanket. In smooth stone dungeon and generic mining tunnels? Not a lot of food or water here.
Of course- this only applies to traditional dungeons. Hex or city-crawls are brimming with opportunities for food- from foraging to hunting. Personal take- high towers or "vertical" dungeons like mountains have water being common, but food is more scarce. Then again, dungeons or deep caves should have more water, just less clean water, so unsure on this one.
Ammunition
Obviously spells and ammunition (either for actual guns or arrows and bolts) are a big part of the resource management. You typically have to have more risk to use a sword up close, but swords don't run out. (Equipment is also a resource too though- that's later).
Resupplying ammunition in dungeons requires some creativity. Personally, I'd allow skilled characters (dwarves) to identify nitrates in caves or soils to be used to make shitty black powder, and probably even stuff a gun barrel with little gravel flakes as an improvised form of ranged attack. Arrows are more complex, but you can probably imagine making arrows out of mushroom wood + underground birds for plummage, with arrow heads being easily reused. Ammunition made in dungeons is probably of pretty poor quality- the main cost here is time. Realistically speaking, unless you're spending multiple days or weeks in a dungeon, it wouldn't be worth the effort to try and hunt down all the materials you'd need to make arrows.
Ammunition is very easily recouped from intelligent enemies however; both their camps and patrols (goblins have shitty arrows, orcs have crossbows, drow have good arrows, bug people have bombs, and so on). It is probably one of the easier resources to recover if you aren't in a naturalist dungeon (cave) or an undead dungeon where everything is old and rotting away. If there are no intelligent monsters in the cave that use humanoid weapons, then you're screwed.
I'm also a big fan of magic rods as a type of "ranged magic weapon" to replace infinite use cantrips. They shoot magic blasts and are essentially a reskinned bow or sling for magic users. If you go with the lore of them being topped with a gem to be used as a power source, then this is a really easy method of resupply- just put a gem you got as treasure on the rod and each shot drains a certain amount of its value as the gem loses luster and eventually turns into a pebble if its all expended.
Spells
Spells are a tricky one. With such a massive part of the game balance being based on resource management, and Magic-Users being so reliant on spells- which are essentially their methods to solve problems at the cost of being very limited.
In some games, spells can be regained through studying your spellbook after either eight hours of rest (possible but difficult in most adventure situations / dungeons), or by studying your spellbook again after casting your magic dice/spell points, or what not. Further games have secondary mechanics- risk reward of casting extra spells past your "safe" limit but at the chance of screwing everything up. However, these methods of gaining extra spells do not count from resupplying in a dungeon itself.
The power gained by spells (instant problem solutions) can be "resupplied" in dungeons through finding scrolls, magic wands, or other magical loot in a dungeon itself. Chopping off a fetish from a defeated kobold shaman and being able to use his remaining spell he had prepared before you killed him is a fun concept- as is having yet unknown and unidentified spells scribbled on walls or stored in little glass balls. The only clue on what it does is a few random words- is it safe or will it blow you up?
Side note: "Spells" in the form of instant use solutions, not necessarily related to combat, are also somewhat "resupplied" by needing less of them over time. For example, you don't need to use Levitate to reach a high platform once you tie a rope around it and can now climb it easily.
Health & Cures
Health is one of the most important aspects to resource management. It is the primary "resource" of martial/fighter-type classes, and important to every character. Dungeons can't give back too easily, or else one of the biggest pressures for getting in and out is removed. Many rulesets allow for short or long rests to recover some amount of health, or using limited use spells or abilities like lay on hands to recover HP.
Other ideas; friendly NPCs in the dungeon that will heal you in exchange for something else. Healing potions are an easy one. Healing fountains stuck in the dungeon make a nice static location where healing can be done; but there has to be a good reason why you can't just bottle the water or swim in it- maybe mutations if you use it more and more. If a dungeon is built or famous for a famous treasure, you restore +1d8 HP or "Grit" just for touching it like a pure morale boost. This helps since it will almost always be guarded by the most dangerous monster.
As for first aid and medicine- I've already written a whole post about it.
Also; the concept of certain stats or your level being damaged (level drain) could be tied under health. Typically, these aren't easily cured in a dungeon and are instead related to the overall campaign and bed rest. An extra rule, like laying a ghost's physical remains to rest cures you of its level drain, might be a nice way to allow players to resupply in exchange for doing something difficult and karmic in universe. Curses get an extra bit- Arnold likes curses that you can cure by doing shit- make the dungeon harder for yourself to remove a penalty.
Equipment
Dungeons contain traps and situations that consume equipment- prybars break eventually, wooden doorwedges are thrown away, and your swords are eaten by rust monsters. Recovering equipment in a dungeon is simple; stealing it from the monsters and corpses here- perhaps even your own fallen party members. More recent corpses probably have better equipment, and anything you steal from monsters will be of poor quality, trapped/cursed, or both.
Creating new equipment or doing advanced repairs to serious damage is probably out of the scope of the timeframe and skill of the characters in a dungeon; but characters of a specific race or class might be able to do so. I like dwarves or gnomes, or those of magical artificer classes, being able to repair anything related to their professions in one exploration turn of downtime. Metal plates may also be stolen from various environmental pieces to patch yourself up; the classic wooden barrel lid as a shield. Why does nobody just use the armor that the animated suits of armor puppet around after you break them apart? That shit is expensive. Snailpeople can just put themselves into a new shell if they manage to find one- that's a good reason for adventuring.
Manpower / Numbers
People will die or become lost/run away as you explore the dungeon. This applies to player characters to a lesser extent, but is mostly related to your hirelings and followers. Link and lantern boys, porters, thralls, whatever- all of them perform useful labor that isn't realistic for a small party of individuals to do; like tear down barricades or haul giant gold bricks out of a dungeon. Some treasure may become totally unable to be recovered if you don't have enough people to carry it, but group size is self mitigating; too many hands means not enough coins, and larger groups tend to use up more resources and attract more wandering monsters.
Groups of people also have other advantages; taking turns on watch, being able to carry each other, etc. It's similar to Kenshi; if enough people get downed in that game and you can't carry them away is when situations quickly spiral out of control- as long as you have enough healthy and strong people to support the knocked out ones, you can remain as mobile as possible.
Manpower is hard to recover in a dungeon on purpose; fresh meat is found back in town, at the tavern, but there are some methods. The classic of finding an imprisoned or lost person in a dungeon to act as a replacement PC could just as easily work for a retainer. I also like the idea of pressing a random goblin or other mook to join your party and do dangerous or demeaning tasks- though this comes with the explicit cost of knowing they will betray you at the first opportunity. More honorable creatures, like orcs, may offer to aid you as a group in exchange for performing a task for them first.
Of course, all of the examples above are for replacing dead or lost party members with new ones, not bringing back old ones. Health is already covered above and resurrection magic tends to be too high of power and scope for being "resupplied" in a dungeon. However I could see very dangerous dungeons having "soul fountains" where the last dying breath of a person (trapped in a bottle of course) can be brought and they will be reborn within a time limit. Or a really haunted place having the ghost of the dead PC being able to be brought back- but they'll need a new, living body. Have them possess a random animal or monster for funsies.
Time
The one thing you can't get back. Time is a "resource" that (probably) can't be recovered in a dungeon at all, but thankfully isn't a problem in every dungeon. In this case, it's less "time" and moreso a time constraint mechanic. Toxic spores that get more dangerous the longer you inhale them, a dungeon slowly sinking into the mud that will soon be submerged in 1d4+2 days, or needing to get someone or something out of the dungeon very soon, else a catastrophic event will happen.
However, "time" as a resource could be returned either with super high level magics (timewarping? Rope trick?) and relating it to the fiction. I could see a campaign where killing high level cultists slows (but does not stop) the return of an elder deity, so taking a detour to search every cultist hideout becomes a valuable way to recover your "time".
Surprise
While only a vaguely resource in a quantifiable sense, the element of surprise could be a significant resource to a party when first exploring a location. If a location is heavily guarded or has at least one intelligent faction there; every time the party fights or is spotted it will be more and more clear that adventurers are coming to plunder or mess up their plans. In that regard surprise becomes like a resource; traded in when you fail stealth rolls, and making future encounters more difficult as enemies prepare for you.
Surprise cannot be recovered once directly lost, but it can be mitigated. Killing guards who spot you before they raise the alarm, covering your tracks with branches in the mud, or waiting a long time before returning to the dungeon to let their guard back down are all valid ways of regaining or preventing loss of surprise.
Confidence
This resource is totally meta- player attitude. Confidence is something that is a direct resource that is expended while a dungeon is explored, but isn't on your character sheet. In a way, the desire to take risks and explore is a resource that is slowly used up as other resources are lost- optimal and safe become more important and socially enforced as the party's position becomes more precarious.
Confidence and time (real life time) is highest when you begin a session- which usually includes a return to the dungeon. From here, the knowledge, mapping, and accumulated player power from progression acts as a sort of boost for confidence, until new areas are explored. People can only go so far before a cautious retreat is in order; especially if loaded with treasure. Winning battles and finding more treasure regains confidence, but also increases risk. If your dungeon is properly large, players may not even explore the whole thing once the cost to risk ratio of remaining treasure and acquired treasure becomes too costly to keep exploring!
This isn't a bad thing though; players not exploring an entire dungeon leads to a mystery and a more "realistic" mindset that treasure hunters would really have; once they've got the hoard, it isn't worth the time and effort to go scrabble for the last few gold coins. The unique values of OSR play make resources especially important and lead to gameplay that isn't just a set up and resolve using the most optimal combat methods your players know; it means the ability to be further invested in the fantasy space- any way players can use their own intelligence and skill to let them stay in the dungeon longer is a direct continuation of that idea.
