Been listening to a lot of video game music at work recently since I gotta in front of a computer all day anyways.
This website https://downloads.khinsider.com/ is super good for downloading video game ost's and listening to video game ost's in order of the album without dealing with youtube for tracks. It's also good for discovering new ost's.
Unfortunately it doesn't have newer video game tracks like songs from undertale due to fact that it serves as an archive for songs.
This site here http://www.smashcustommusic.com/ might sound like its only for putting custom music into smash bros (which it does do). But it's actual best functionality is its innate ability to loop songs seamlessly with having to deal with "extended versions" or youtube repeat https://listenonrepeat.com/ .
However it doesn't have every song out there.
I'v been listening to fire emblem music and jrpg battle themes like dragon quest 9 and Bravely Default recently.