Joplin only works in terminal--no gui

You have installed two versions of Joplin, the terminal app and the desktop app. They are independent and do not share a database or config.

joplin will lauch the terminal app, to launch the appimage from the terminal you should execute the full path of the joplin appimage.

I have a strong suspicion that you don't have fuse2 installed - see this thread and post:

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