I‘m not sure if I‘m missing something, but I‘d be really surprised if Volition was doing fine. Agents of Mayhem didn‘t do well at all and the Saints Row reboot was pretty terrible. Their last somewhat successful launch was probably the Saints Row 4 expansion back in 2015.
It‘s always sad to see a developer shut down, especially one with such history. But I can honestly understand closing a studio which hasn‘t had any great release for over eight years.
Flatpacks are very restrictive by design. While this is a good thing in many cases, it makes it very difficult for tools like EmuDeck to work properly. For example, automatically installing other applications (in this case: emulators) isn‘t easily possible. This would make a flatpak version of Emudeck pretty much useless.
While I understand your concerns, I think installing an AppImage which has been built on Github from open source code just isn‘t all that risky.