Appimages are bloated and unreliable. You can't guarantee that your app will run on any machine because it might depend on different system libraries.

Flatpak uses shared stable runtimes that are the same everywhere and don't take up space more than once. It also comes with a native update system and sandboxing. Snap is the same thing but worse.

AppImages do not work anywhere close to how macOSs .apps do, and even if they did the approach isn't correct for how things work on Linux.

I'll avoid it at this point anyway. The Rust coreutils is another reason for that. Snap, monetizing updates, telemetry, enough is enough.