There's a few games I didn't know about and/or have yet to try on this list
It took me months to dig up half of the games on this list on my own, and although I do know some games that aren't on there, that's the best list of foss games I've found so far.
@Naughtylus Thanks for sharing! Will have to refer to that the next time I get the feeling there are not many high-quality FOSS games out there.
Fosstodon is a Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.