Hey Theo, thanks for looking into this. I tried your suggestions --- running the AppImage with the "extract and run" option produces the same result, and I already have libfuse2 installed. So I'll wait on this and check back here tomorrow.
OK, this was a doozy. I uploaded a new a super solid appimage that works in mint 21.3, full instructions in the readme. If you're using a high density retina display, the window might be significantly smaller than designed. Spent all day trouble shooting it. But a full fix for window scaling will have to wait till v1.2. If you're using a 1920x1080, display, should be perfectly fine!