Got somewhere :-)
Tried to launch game by moving its launcer behind sudo command in terminal.
No luck - it was actually rather weird.
Then i tried launching it with start.sh file in game directory from file manager launched as a superuser.
Guess what.
Game started with all settings in default and i was allowed through the
door. :-)
It might be related to the "reset setting" suggestion from your troubleshooting guide....
However your guide could use some more info how to actually do it in linux really dont know where "the game's save directory" is located.
will report if anything changes.
EDIT:
So far so good, got to the part - that is just after area where Carl is located, without any problem.
I would say it looks solved.
...*sigh* i feel like i am talking to myself here. :-)