I can confirm that it is a problem with a vanilla Ubuntu 22.04 LTS install.
Downloading the appimage and attempting to launch it does nothing at all.
If you launch from terminal:
$ ./Joplin-2.7.15.AppImage
dlopen(): error loading libfuse.so.2
AppImages require FUSE to run.
You might still be able to extract the contents of this AppImage
if you run it with the --appimage-extract option.
See https://github.com/AppImage/AppImageKit/wiki/FUSE
for more information
One approach here could be a modification of the joplin_install_and_update script to check for libfuse2 and prompt the user to install it first before trying to launch Joplin (or make the user run the script again to ensure they don't just ignore the warning and try to start it anyway).
Not sure what can be done about the "plain" appimage download as it gives no feedback at all.