Besides the already named ones, here a few:

• endless sky: Inspired by a game called escape velocity. You fly around in a spaceship and do space adventures.
• naev: Similar to above, but quite different.
• ddnet: Multiplayer coop 2D platforming. (Has enough active players.)
• warzone 2100: Real time strategy with tanks. Has a campaign.
• battle for wesnoth: Medieval turn based strategy game.
• mari0: 2D mario with protal gun.
• mindustry: Build factories and defend against enemies.

https://forgefed.org/

The Digital Markets Act: https://en.wikipedia.org/wiki/Digital_Markets_Act