The three existing Linux distribution-agnostic software package managers I’m aware of are AppImage, Flatpak and Snap. There may be more I’m not aware of, although I seriously doubt it. As far as I know, all three will work with almost any Linux distribution. There will always be outliers, of course. Therefore, I really can’t guarantee anything.
Of the three formats, AppImage is the most flexible. Any user can give an AppImage software package the ability to execute. There isn’t a good central repository, like what the other software package managers have, and it can take a while to find what you’re looking for.
The AppImage format was originally called “klik” when it was invented in 2004. I didn’t discover any of them until 2019, long after the latest name change.
I first found AppImage packages at the Electron portal and I really don’t remember what I was looking for at the time. You can also find them at AppImageHub. AppImage packages don’t have to be listed at either place and I’m sure you can find them elsewhere. In fact, the sync client for pCloud can only be found at their site.
AppImage files can be stored almost anywhere. I usually store them in a dedicated directory under the home directory (when I’m actually using any).
The Flatpak format is widely supported. It originally came out in 2015, under the name of “xdg-app”. Some Linux distributions support it out-of-the-box. Linux Mint has supported it since version 18 (and I’m using 20 now).
Flatpak packages appear in native software managers as well as at the main Flathub repository. I don’t know where else they can be found. When installed, a directory for it appears in the user home directory. Even when you uninstall, the empty directory (or a directory with leftover non-executables) will remain. As far as I know, I’ve only installed one Flatpak application.
The Snap format is wholly controlled by Canonical, the company behind the Ubuntu Linux distribution. Canonical also maintains the Snapcraft store. Of the three software package managers, Snap seems to be the hardest to use (at least to me).
If I’m not mistaken, all the Snap packages are stored in a single Snap directory. I never found them elsewhere. Linux Mint 20 doesn’t support Snap due to some backend shenanigans concerning the Chromium web browser.
Linux distributions have various package managers for various formats, sometimes including those I previously mentioned. Debian, and distributions based on it, install packages with the “.deb” file name extension.
Most package managers are fairly up-to-date. Sometimes, however, they lag behind because the developers responsible for maintaining certain packages can’t keep up for various reasons. Like certain AppImage packages, some Debian packages have to be obtained from the source websites.
The KeeWeb password manager Debian file is only available at the KeeWeb website (well, the last time I checked). Since the software is frequently updated, it doesn’t make sense for a repository “middle man” to work with it as well.
I prefer native packages when they exist. That is, unless they’re several releases behind the packages at the source websites.
Image Attribution: Peter Simon / Public domain
Edited and updated. Originally published at one of my other websites in June 2020.