Played 0AD recently, which is a RTS like Age of Empires. You can play it multiplayer on LAN too. It's quite fun, though my base constantly gets burned to the ground by at least three different armys simultaneously
For shooters: Red Eclipse which is also available on Steam. If you go there, choose the beta Version, since the initial release on Steam from 2019 isn't really good. I guess you can play the beta too, if you clone the github repo and build it yourself.
Both are available in your linux distributions repositories. Red Eclipse is quite old there though (version 1.6, Steam: 2.0)
There are also a slightly old OSS Counterstrike-like tactical shooters like Urban Terror and Assault Cube Reloaded I enjoyed in the past.
Most of the FOSS shooters I know are based on the Cube-Engine. I'm looking forward on something based on the Godot Engine. Maybe there are some more games to be released as FOSS in the future
I imagine that developing a opensource game is a very tedious task for the main devs. After all, games are not just code but also textures, 3d models, animations etc. Difficult to keep a vision when 100 people all over the internet are committing to it.
Just the community I needed to find! I was literally about to close lemmy to go look for open source games and ports for Android.
I started Shattered Pixel Dungeon and was having a lot of fun with it. It is the first real Roguelike I think I have gotten into. It takes a bit of learning, but it still feels pretty accessible. Definitely worth the free download to see if you enjoy it