Bug 512982

SUMMARY
Please add support for AppImage files management (view, install, uninstall) to Discover.
Install should do similar things that it does for other packaging formats, copy the files somewhere and create shortcuts to them in the main menu.
And uninstall should do almost the reverse, similar things that it does for other packaging formats.

STEPS TO REPRODUCE
1. Download a program in the .AppImage format from one of the links in the OBSERVED RESULT or other sources.
2. Try to install it with Discover like you can with other packaging formats.

OBSERVED RESULT
Trying to install any of the programs below that you downloaded in the .AppImage format because it was the only one available or because you like it or because you don't currently have an internet connection for the others:
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Signal (Beta) + Session desktop messaging clients and SamRewrittem Steam Achievements Manager are available  only in AppImage:
https://community.signalusers.org/t/beta-test-the-signal-desktop-linux-appimage/73330
https://getsession.org/download
https://github.com/PaulCombal/SamRewritten/releases/tag/20250919.1

The Moonlight Qt (the client for the Sunshine remote desktop), for Linux, other than the awful tar.gz,there is only AppImage:
https://github.com/moonlight-stream/moonlight-qt/releases/tag/v6.1.0

SimpleX messaging client, other than the .deb, there is only AppImage:
https://github.com/simplex-chat/simplex-chat/releases/tag/v6.4.7

The QTox messaging client, other than Flatpak, there is only AppImage:
https://github.com/TokTok/qTox/releases/tag/v1.18.3

Trifa Material messaging client, other than the .deb and .rpm, there is only AppImage:
https://github.com/Zoxcore/trifa_material/releases/tag/v1.0.56

Wire messaging client, other than tar.gz and .deb, there is only the AppImage:
https://github.com/wireapp/wire-desktop/releases/tag/linux%2F3.40.3718

VeraCrypt encryption management, other than tar.bz2, .deb, .rpm , there is only AppImage:
https://veracrypt.io/en/Downloads.html

Heroic game management, other than tar.xz, .pacman, .deb and .rpm, there is only AppImage:
https://github.com/Heroic-Games-Launcher/HeroicGamesLauncher/releases/tag/v2.18.1

Most important | popular browsers also have versions in AppImage:
https://github.com/srevinsaju/Firefox-Appimage
https://librewolf.net/installation/linux/
https://ungoogled-software.github.io/ungoogled-chromium-binaries/
https://github.com/Alex313031/thorium/releases/tag/M130.0.6723.174

Front-ends for popular websites:
https://freetubeapp.io/#download

OnlyOffice:
https://www.onlyoffice.com/download-desktop

Stellarium (Snap and AppImage):
https://stellarium.org/

MKVToolnix program for management of Matroska, while it comes even natively in the repository of many distros, for the others it has a dedicated page section for AppImage files:
https://mkvtoolnix.download/downloads.html#appimage
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It's impossible as Discover just doesn't support it!
And it's also impossible to manually make it support it because there is no AppImage back-end!
 Like there are for Flatpak and Snap formats.

EXPECTED RESULT
I expected, that like with the native (.deb in my case) , Flatpak and Snap formats, the AppImage format to be supported too.
Especially since if you look at the above programs, by following the links, the AppImage format is at least as popular as the native ones or Flatpak and Snap formats.
In some cases, like in ones for Signal, Session and  SamRewrittem, the AppImage format is so popular, that it's the only one provided, so it's actually more popular than all the others.
While in other cases, like Moonlight, SimpleX, Trifa Material and Wire ,it's the only other alternative to the tar.gz or .deb | .rpm.
As for rest of the cases, it's just available along with Flatpak and Snap
Because of that I consider it at least as important as Flatpak and Snap, and I expected it to be treated with the same level of support.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 6.5.3
KDE Frameworks Version: 6.20.0
Qt Version: 6.9.2

ADDITIONAL INFORMATION
While I understand that the AppImage format has not been designed to be installed from day one or at all, it doesn't mean that it cannot be done if someone wants to do that or that the design / specification of them forbids that.
This format and the fact that it's just one file has 3 great advantages:
1. Easiest portability (everything contained in just one file and most of them work just by running them).
2. Easiest back-upping / restoring (just keep / copy all the Appimage files that you use somewhere and back).
3. Easiest restoring offline. (something that is extremely hard with the others, especially with Flatpak).

So, what I think would be best is the following:
1.  When I right-click on an .AppImage file I have the first or the second option "Open with Discover (like for the.deb and other formats) files.
2. Then after I see in Discover some information about it, I have an "Install from..." button in the top-right corner, like for .deb and others.
3. If I click on that button, then it should do something similar to the .deb files, like copy it somewhere and make a .desktop shortcut for it in the main menu (Kickoff) and remember that I have installed it so I can uninstall it, which should just delete it from where it copied it and remove that .desktop shortcut to it from the menu and from the ~/Desktop, if I added a shortcut there too.

Additionally it would be nice to have an option in Discover to specify a folder where we keep all our .AppImage files that we want installed (having shortcuts in the menu) that should dynamically add or remove .destkop shortcuts for them in the menu (and when they disappear from the menu, they should disappear from the ~/Desktop too).