Antoine If you're using Steam flatpak, you need to install FLATSEAL. Flatpak will essentially sandbox your app, in this case Steam, and the games you launch in it. Flatseal lets you change the permissions of all installed Flatpak apps. I'm not sure which permissions specifically, but they're likely the ones to do with file sharing and allowing access to your local folders.
I'd use the repo version of Steam, far less issues.
