skimming through my games, spam incoming...

obra dinn takes place on one boat
9 hours 9 persons 9 doors also takes place on one boat. actually all the zero escape games take place in contained facilities, although for the others what the facility is tends to be a spoiler
also danganronpa 1 and 3 are both in contained schools. 2 technically is also in "one location" but it's multiple islands in the ocean all of which have distinct identities so it doesnt really feel like it fits
death come true is also all in one hotel. this is a common theme in death games it seems
umineko mostly takes place on rokkenjima island. definitely plenty of flashbacks off the island which might disqualify it but it's probably like 90% on that one island and it's 100 hours long so you spend a lot of time there
it takes two takes place in one house
does firewatch count? you wander around a lot in firewatch but it's all anchored to one lookout tower and the area immediately around
dr. langeskov is in one building
the vn "password" is like 50 hours long and entirely in one mansion/the immediate area surrounding it
dear esther is on one small island
tacoma is on one space station
why am i dead at sea is on one boat
murder of sonic the hedgehog is on one train
little inferno takes place pretty much entirely sitting in front of one fireplace
if you're including portal may as well throw in narbacular drop too
i spy spooky mansion is in one mansion
the, uh, garten of banban games are all in one facility too lol

obviously maybe not all of these games apply, i also limited this by assuming there was some narrative something going on, i.e. there are a lot of job sim games that are just in one building but those don't really tend to have much of a story and don't really feel like they fit in with the other games here

trying to think about this as quickly as possible, a few flash art games like no-one has to die (2013), bars of black and white (2009), the majesty of colors (2008), the day (2010) are easy candidates. maybe You Have To Burn The Rope or You Only Live Once too lol
all the main series tokyo xtreme racer games take place on one small highway system but the only one with a real narrative is import tuner challenge
eternal quest (2004) takes place in one long dungeon, im sure there are a ton of other dungeon crawlers like that tho
skyscraper (2008) takes place entirely within the titular skyscraper
the desolate room takes place entirely in a crash site, the desolate hope is confined to a space station but you go into simulations and that creates different environments even if the part of the game set in the "real world" is physically confined. if half life is here with Xen then i dont see why not lol
following that logic i had to abstain from any "but it was all a dream!!1" games
also aping off of tdstr's suggestion of little inferno, Human Resource Machine takes place in an office

Thank ya'll so much!

@tdstr
"i also limited this by assuming there was some narrative something going on"

This is ideal for me personally because some of my favorite games like Control, Prey, etc. are the kind of ones I'm looking for! A narrative/single player story adventure that takes place in one location for the most part! I'm accepting of some things like Half-Life's Xen that is a small part of the game, but at least 80-90% of the game is in that one location!

Thank you as well @inbox for the recs! Added them in as well :)