Small list from me:
Dungeon Crawl Stone Soup, Caves of Qud, Cataclysm Dark Days Ahead, ADOM, Reigns, SanctuaryRPG: Black Edition, King’s Quest, Liberal Crime Squad. The old Elder Scrolls Arena and Daggerfall are also currently available for free. I see Daggerfall is playable with DosBox/Lutris, I assume Arena is as well.
Small list from me: Dungeon Crawl Stone Soup, Caves of Qud, Cataclysm Dark Days Ahead, ADOM, Reigns, SanctuaryRPG: Black Edition, King’s Quest, Liberal Crime Squad. The old Elder Scrolls Arena and Daggerfall are also currently available for free. I see Daggerfall is playable with DosBox/Lutris, I assume Arena is as well.