Problem: Trying to create a new character in single player mode, you get the error "Generic bad character: this character will not work with this version of Median XL." The docs say this problem occurs if 'User Name' in the users folder (C:\Users\<USERNAME>) has non-latin or "special" characters in it. But my username was all simple Latin chars.
Workaround: Host a game in TCP/IP mode and create a new character, then switch to single player mode and play the character from there. No more errors. I can now create new characters directly from single player mode.
Hope this helps someone else out!
Running in Wine 5.0 on Kubuntu 18.04.4.