As a new poster I’m not allowed to reply more than twice per topic (crazy)! But I have fixed my issue posted here Ubisoft Connect does not start (black window) - #7 by praz01…
I’ve fixed this by removing and reinstalling Ubisoft Connect using the Lutris wizard. During the reinstall noticed the wizard failed with Winetricks configuration, complaining about preexisting config. It looks like you can’t just switch between runners without doing a bit of housekeeping and need to delete the prefix folder first to remove stale installations, is my guess. Everything worked perfectly after that! Hope that helps others.