@itsuko @alexandra @Seirdy
Oh, c'mon. You can *warn* a user to not do stupid things like installing apps from unknown sources, but you should not entirely deny it.
Assume, it would only be possible via command line. That would be absolutely ok, and would protect beginners.
The thing is, people that hang out in PP chats, download and install packages are not beginners.
Flatpak can not protect you from not using flatpak.