@Aslain Sorry, no logs found. I used the de-installation exe plus deleted content of the res_mods folder before I realized about the possible conflict. Then I did a new install without the region changer.
When I use the WGC login, I have to hit enter to join, while Champi's autologin directly joins the server.
Just an update about this thread related toward 'gun engine and sound mod' thread, where the solution is to be found.
One using Lutris/Wine has to install the Aslain modpack exe from within the container, where the game-files are located.
Writing that link down is also the path to the solution for this issue.
Thx a lot @Aslain and @angulion for helping me out solving this issue. Great modpack and excellent support even for the small Linux party!
Kepos's post in Region changer plus Champi's autologin fail to authorize was marked as the answer