Comment 3 for bug 2004482

This is caused by ubuntu's package uaclient having the same name as https://github.com/FreeOpcUa/opcua-client-gui Uninstalling opcua-client with pip allowed software-properties-gtk to run.

I've had opcua-client installed for a long time without any problems. It probably started here, where the Ubuntu Pro features got activated: https://git.launchpad.net/software-properties/commit/?id=1ee752c22956248ffffa8ce84c753bce32b18041