I'm on an Ubuntu 22.04 Desktop computer. I click on the big green Free Download button. It downloads a .tar.bz2 file. I double-click on that in the Firefox download manager. It opens the Gnome archive extractor. I'm looking at... .gif files? .so files? I see something called "thunderbird" and another thing called "thunderbird-bin". I double-click on those and some other dialog pops up that says "No applications found for 'thunderbird'".

Will desktop Linux ever solve these basic usability problems?

Or will this always just be user error! you're doing it wrong!

It has. AppImages work exactly as a user would expect them to. Even if the AppImage is not marked as executable, one of the problems I can imagine a new user encountering, Dolphin (KDE file manager) asks if I want to trust and run the file anyways.

It is on Thunderbird for just distributing a weird tar file. Preferably, their download button would take you to an installation instructions page.

And idea how to get Dolphin to "register" the AppImage as an application? (so it shows up in menus). Manually making AppImage .desktop files is always a bit clunk and you don't get the proper icons. I know there is some thrid party tool that does it more properly, but I wonder if there is an integrated way

I swear this used to work automatically and at some point it was removed.. or maybe I'm misremembering