Haven't seen these two so thought I'd add them to the list.
Minetest is a block building game engine (like minecraft) built around the idea mods add all content. There are a bunch of games built for it, and last I checked a active modding community.
https://www.minetest.net/
The other is AlephOne, a engine to play all the Marathon games (story FPS, pre-halo bungie made games) along with a bunch more community created ones. I've sunk a good bit of time into both the trilogy and the additional 6 big community made ones.
https://alephone.lhowon.org/
Minetest is a block building game engine (like minecraft) built around the idea mods add all content. There are a bunch of games built for it, and last I checked a active modding community. https://www.minetest.net/
The other is AlephOne, a engine to play all the Marathon games (story FPS, pre-halo bungie made games) along with a bunch more community created ones. I've sunk a good bit of time into both the trilogy and the additional 6 big community made ones. https://alephone.lhowon.org/