I'll be honest: at this point, I wouldn't blame anyone for not worrying about providing support for pre-2.0 PyQt5. Just leave a version that still works with pre-2.0 Sigil and make a new one that works with PySide6. With the AppImage and the ability to use virtual Python environments for plugins, there's very few people that can't get PySide6 available for Sigil plugins.
Of course anyone who wants to continue using plugin_utils as a compatibility layer between the old and the new will receive bonus points!
