@James
Thank you for the the updated (SP50) version.
I discovered a couple of bugs:
1. Broken menu options: Options->User Interface->Advanced/Researcher/Manufacturer. Does not change the UI.
2. When uploading config with a conflict in a theme (eg. conditions must have the same size), the app just crashes while Windows version provides a dialog describing the conflict.
Other than that works like a charm.
Running on Ubuntu 22.04 (Mono 6.8.0.105+dfsg-3.2, GTKSharp 2.12.40-3ubuntu1, GTK 2.24.33-2ubuntu2)