https://bugs.winehq.org/show_bug.cgi?id=43995
--- Comment #5 from mi.bar.2001@gmail.com --- (In reply to debianxfce from comment #4)
Remove UplayCrashReporter.exe from the .wine/drive_c/Program Files (x86)/Ubisoft/Ubisoft Game Launcher/ directory to fix this bug. The game works fine without it. Backup your /home/xfce/Documents/Assassin's Creed IV Black Flag/Assassin4.ini file, some display setting can cause a black screen.
Unfortunately this didn't help. The game still won't start. I attached a new log file (removedUplayCrashReporter.log)