@ceruds @JapanAnon @BackupHitter Open source: 0AD*, minetest*, Pokete, portable puzzles, Veloren, Open Riichi*, Urban Terror, Unvanquished, Endless Sky, Xonotic, Vintage Story(?), Linwarrior.
etc.: Din's Curse/Zombasite*, Gens, Sins*, WC3 (SWAT: Aftermath*, Terrania*), Trails of Cold Steel, Disaster Report, Avorion, Evochron, Lemma, Stranded.
No online requirement, mostly no DRM, no VNs, no hentai.
Everything marked with a star is something I'm actively looking for people to play with.