appimage, snap, flatpak, backport, when to use which?

[Marco Moller <mmoller@cicbiomagune.es>]

Hello,
I try to understand how and in which situation the established users opt for the usage of backports - and why meanwhile years old methods like AppImages (or quite new ones like Snap and Flatpak) are nowadays not routinely used instead. Don't get me wrong, I am not pushing against backports, I simply try to orientate myself while digging deeper and deeper into the world of Linux and Debian, and became confused.

Is it because backports are centrally installed for all users, while the other options are to be duplicated for each single user?
I would not expect that there is a numerous demand for backports of "optional" or "extra" packages, and therefore would also not expect the updating local installation of those packages in the user's home directory to be massy. Most of the time users in search for most up-to-date packages are anyway not working with the "stable" distribution, but would right away stay with the "testing" distribution. I do see the advantage of backports when it is about the treatment of "essential", "required", "important" or "standard" packages, though. Following the philosophy of that classification, those packages to me appear better hosted centrally in the system, and not on a per user base. But updates to "optional" and "extra" packages, wouldn't this be first class candidates to become addressed by an Appimage, Snap or Flatpak package, also if an update to an "optional" or "extra"  package would subsequently need an update to a dependency out of the "essential", "required", "important" or "standard" packages? These "app containers" are in the end designed to specially care for exactly this situation to also bring the needed dependencies, or?

Is it because a package maintainer should not carry the burden to also monitor possible issues in the dependencies by publishing the package update as a backport, and not having to provide and not having to care for the dependency as well?
I would be surprised if this would be much hassle, expecting that the maintainer would only have to release a new app container if indeed such issue in a dependency would occur and once be fixed by the maintainer of the dependency package. Here, AppImages might indeed be more risky to provide, because of the missing mechanism to reach users with important updates to it. But Snap and Flatpak do autoupdate themselves, if I understand correctly, and thus appear to be the more modern approach to deal with this situation of providing updates to "optional" and "extra" packages for the "stable" distribution, or?

Regards, Marco.