@itsfoss I hate the mess AppImage makes. It's basically equivalent to just unzipping its files into a temporary location every time you run it.
Snap is... an arbitrary system owned by a company that I don't really trust long term and even short term has disadvantages like being slower to port stuff, less frequent with updates, etc.
You forgot Docker. My problem with it is also the fact it's owned by the sort of company you can't 100% trust with a lot of proprietary stuff.
Flatpak isn't perfect. What I truly wish to see would be some sort of containered sandbox that is more clean and open than Docker. Flatpak is... not really that, but it's the closest we have at this time I suppose. It's also fairly open as far as I'm able to tell and has pretty good support from a lot of people.