

If you care to trust random strangers with your secure messenger that’s a choice you can make (admittedly the desktop isn’t particularly secure to begin with but even more reason to use the actual org’s build imo). I’m sure christian heusel is very reputable.
My os does not do that
I don’t consider “wanting a secure app to be installed through first party means” to be particularly unusual. I know in Linux it’s standard to just install random stuff from the internet with root. I’ve obviously done that myself, but for secure stuff I want first party. Making a flatpak wouldn’t be hard (they probably just need to review someone else’s work – it’s like an intern project)