FlatOut: Ultimate Carnage Save Game Location
Windows
FlatOut: Ultimate Carnage save games can be found on Windows here:
C:\Users\[user_name]\AppData\Local\FlatOut Ultimate Carnage\Savegame\
Linux
FlatOut: Ultimate Carnage save games can be found on Linux (Proton) here:
~/.steam/steam/userdata/[user_id]/12360