You can install an application like Flatseal (flathub.org/apps/com.github.tchx84.Flatseal) to inspect the permissions for a flatpak.
How locked down a flatpak is depends entirely on the developer and what permissions they request. By default, they can’t really see much. For example, they can’t even see the processes running on your host or your user and system files.
Flatpak does not do anything about network access though, it can only do no access or full access, no in between. The data they can collect on Linux in a Flatpak is very limited but it does not prevent them from calling home.
FauxLiving@lemmy.world 9 months ago
Without using exploits to escape the container, not much. A very empty Windows environment with a single game installed, your network interfaces and any directories that the Flatpak has access to (usually just the SteamLibrary directories).
The TOS (www.take2games.com/legal/en-US/) changes are mostly related to data that they collect via their interfacing with Steam and through their website. This idea that they’re requiring you to agree to a root level access or installing a spyware rootkit are just nonsense.