I saw multiple issues reported on this topic, but none solved so far (search by "uplay"), therefore creating a new one. I have a Linux (Fedora 43) with Heroic installed both as a flatpak and RPM-based application. Both options produces the same problem: as a user I authenticate in Epic Games Store, download a game and when launching, it hangs on pop-up window from Ubisoft Connect saying "logging in". Logs and screenshot are attached.
What I noticed, there is a Linux process that cannot complete and it's definitely related to the issue: C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\upc.exe uplay://launch/353?source=epic&exchangecode=XXXXX&epicuid=XXXXX