Did you figure this out? I have the same issue. I can run the AppImage but since it isn’t properly installed I can’t make it the default when I double-click an audio file.
I think you are saying that the inconvenience is caused by the lack of file associations that come with using an AppImage. Is that right? I’ve just got used to always starting Audacity first and opening the project from within the program.
I’ve just tried this and it worked for me:
Locate any of your Audacity project files and right-click on it. Choose ‘Properties’ > ‘Open With’ and then click on the ‘+Add button’. Audacity WON’T be listed so you have to click on ‘Use a Custom Command’. Click ‘Browse’ and navigate to where you have stored your AppImage file for Audacity. Select the AppImage file and click ‘Open’. Click ‘Add’ on the next dialogue and then ‘Close’. Now, when you double-click an aup3 file, it will open in Audacity. I can’t believe I haven’t tried that before.
There is one caveat - if you upgrade to a later AppImage file, you will have to do this again UNLESS you give it a generic name without a version number in it.