Although our orcs don't exactly follow any particular literary tradition, and are flexible gameplay wise by design, Tolkien is still one of the main references. In Middle earth, orcs were bred at the very roots of the world in the eerie dark pits of Utumno and mostly lived in deep places (Angband, Moria, Gundabad, Misty Mountains, etc.). Just as comfortable below ground as dwarves, fine miners when needed although they'd quite rather pillage and occupy a dwarf site when possible. Some of the tribes were in fact pretty cave adapted and feared or hated sunlight. In Orc Fortress "lore", to the extent that is a thing, this type of tradition is reflected in the Mountain Clans backstory & embark loadout.
Edit.
Although, surface dwelling "Steppe Clan" forts seem to be a forum favorite. Which is great, working as intended that multiple styles are possible. In the new version I am proposing that ironbone (or bonemold, as I'd rather call it) be a little weaker that it was in Old Masterwork so that surface orcs still have incentive to kill & loot invaders or strip mine for iron. What do you all think? Balance wise I think the upgraded organic metal Bloodsteel can still be pretty strong and we can tune for balance how hard it is to craft.