Flathub builds a Skrooge flatpak from its own spec at https://github.com/flathub/org.kde.skrooge/blob/master/org.kde.skrooge.json , and kdeapps checks Skrooge's git master every day for changes and builds using https://invent.kde.org/office/skrooge/-/blob/master/org.kde.skrooge.json .
These occasionally need updating and there are a few outstanding bugs at bugs.kde.org, but you could close this task as resolved.
Snap has been created but is out of date @scarlettmoore
Flatpak is on Flathub and up to date
AppImage doesn't really have a centralised place to store them, and thus distribute them from.
If we want a central AppImage repo for KDE apps it could be hosted on cdn.kde.org but as they can be quite large due to bundling many libraries I'm not sure what the space requirements would be for them or how much space we have @bcooksley
Space isn't too much of an issue on cdn.kde.org:
Filesystem Size Used Avail Use% Mounted on /dev/md1 1.9T 1.2T 631G 65% / none 492K 4.0K 488K 1% /dev /dev/mapper/vg0-archives 4.9T 1.6T 3.4T 32% /srv
We just have to ensure that they are expired in a reasonably efficient manner (and with some kind of sensible naming convention that is scalable). Discussing how to implement all of this is probably best done elsewhere though rather than here.
With regards to Flatpak, you can have nightlies without too much effort there by relocating the definition in your repository to $REPOROOT/.flatpak-manifest.json and then enabling the corresponding Flatpak CI job.
For Appimage, you will need to ensure your Craft Blueprint is up to date then you can add the corresponding Craft Appimage CI job.