The layers (especially mouse layer) is so genius I can't believe it isn't more common
it should have been very telling to the linux community that Microsoft with all its mighty billion dollars wasn't able to force sandboxing on the users with WinRT and had to backtrack and allow Win32 apps again. Hell, people moved to linux because MS tried that.
But sandboxing isn't a requirement on Linux, its an optional distribution method. When you look at a console like the Steam Deck, that system practically requires you to use Flatpaks for third-party software because the OS is an immutable image. If you install anything through pacman it will be wiped on the next OS upgrade.
It is an unquestionable mistake to conflate packaging/distribution and runtime sandboxing into a single solution. These are different problems that fundamentally have nothing to do with each other. There are great solutions for sandboxing that don't care how an application is installed, and solutions for packaging that don't force a specific sandboxing solution on you. This failure to separate concerns is one of the primary disadvantages of Flatpack.
I would agree with you if there wasn't already RPM, debs, etc. But also given how flatpak is implemented on top of containers, it's basically "sandboxed by default" and any unsandboxing involves exposing/mounting things in from the host into the container. You can "unsandbox" any flatpak you want using flatseal (or if you know how, flatpak directly), so I think flatpak is actually pretty good in this regard.
No, these are purely packaging solutions that do not conflate their purpose with sandboxing.
> But also given how flatpak is implemented on top of containers,
Yes, this is the problem I'm referring to.
I think most people don't like AppImages mostly because they don't provide any sandboxing. I think that's a silly reason myself, but I'm also an old, and us olds aren't terrified of using our computers like the youngs seem to be ;-). Though, other OSes are getting sandboxing for applications and Linux needs to not get left behind, so I'm glad it's being solved.
I also think fragmentation is a (valid) reason people dislike AppImage also. It's nothing wrong with AppImage specifically, but that its existence harms adoption of Flatpak by making it easy for people to not use Flatpak. Personally I see them occupying different niches. I use App Images for things like Kdenlive, Logseq, Upscayl, and UHK Agent. Those could all be Flatpaks, but developer effort matters. If devs provide an App Image build I think we should be praising them from the rooftops for caring about Linux!
Another reason is that it clashes with immutable OSes like Fedora Silverblue or SteamOS that are heavily container-based.
What I'd love to see is a tool that takes an App Image and automatically builds it into a Flatpak (possibly with predefined metadata). Flathub could easily be populated this way so that it's easy for developers/distributors to package and ship, but also Flatpak is the standard.