I have upgraded to Nextcloud Desktop Client Version 3.10.0 (Nextcloud-3.10.0-x86_64.AppImage) under Ubuntu 22.04.3 LTS. But unfortunately the main dialog window is corrupted (icons not displayed, cannot move the window or close window). See screenshot attached.
I suppose you already tried to restart and you checked the logs for some obvious issues. In this case, I’d consider opening an issue on the bug tracker yourself. Since the system, affected versions and the symptoms are a bit different, I wouldn’t use the same topic (if it turns out that they are linked, the developers can still link them).