I Created A Desktop File for Linux Users
One of the issues with MuseScore when it installs via AppImage is that it does not create a desktop icon; to remedy this, I created a desktop file that a Linux user can place in their /usr/share/applications folder.
Please look at the file before adding it to the applications folder as you need to include the path to the appimage on your computer and provide a MuseScore logo image (check MuseScore's GitHub for this).
Hope this helps with development! Perhaps this can be added to future iterations of MuseScore, Devs?
Here is the file
[Desktop Entry] Name=MuseScore Comment=Create, play and print beautiful sheet music Exec= Icon= Type=Application Categories=Music;Application; [NewWindow Shortcut Group] StartupWMClass="mscore-portable", "MuseScore3"