Hello @oech3, I am the current maintainer of joplin-appimage. This package is still maintained. As you can see in the pinned comment for this package, I only follow stable versions of Joplin. At the time of writing, the latest stable version is v.3.3.13 (you can check this at => https://github.com/laurent22/joplin/releases/latest). If you prefer unstable versions, take a look at the joplin-bin or joplin-beta packages. Feel free to leave a comment if you have any further questions.
oech3 [1] filed a request to merge joplin-appimage [2] into joplin-bin [3]:
Upstream didn't drop AppImage yet, but this package is not maintained and older than deb
[1] https://aur.archlinux.org/account/oech3/ [2] https://aur.archlinux.org/pkgbase/joplin-appimage/ [3] https://aur.archlinux.org/pkgbase/joplin-bin/