And of course, a few more immediately come to mind:

#Sable
#YokusIslandExpress
#EnvironmentalStationAlpha

Also #Inmost isn't quite in this grouping but it's close. And for completeness sake I should mention a few games that are more well known:

#HollowKnight
#Ori
#Celeste

I also haven't included older/mainstream games, but basically along the lines of #Metroidvania / #JRPG. Special mention to
#Marvelous (Another Treasure Island) which only every got an indie translation to my knowledge and which has done very refreshing mechanics.

So because Mastodon instances tend not to support fulltext search by default, I guess hashtags (which *are* searchable) are that much more important? I.e. every time you mention a game, like #Dysmantle or #MedievalDynasty or #EnvironmentalStationAlpha or #MadeInDreams, you should hashtag it to promote findability and discoverability, as a kind of etiquette...