Same Here, nothing will Help... No Experimental or other Version i tried
Newer versions of Ubisoft Connect work now.
Download Ubisoft Connect directly from Ubisoft's website.
Use protontricks to uninstall Ubisoft Connect and install from exe instead.
proton 8.0-4x1 2023-12proton experimentalx1 2023-12PROTON_LOG=1x1 2023-12
Launching Ubisoft games through Proton results in following error issued by Ubisoft Connect:

So far I've confirmed this error on Far Cry 5 and Watch Dogs using Proton Experimental bleeding-edge and Proton 8.0-4 but I imagine it being an issue on other titles as well.
Logs recorded using
PROTON_LOG=1 %command%: https://gist.github.com/MacTavishAO/e0ef10c76ed075a828a51b3ed94da758System Info:
OS: Arch Linux
Kernel: 6.6.1-1-clear
DE: Plasma 5.91.0 (Plasma 6 Beta 2) Wayland
Mesa: mesa-git 24.0.0_devel.182318.377c6b2d45e.c5c71e7-1
CPU: Ryzen 7 5700X
GPU: RX 6800