The issue happens in the script processing thread while drawing the panel UI, so this problem isn't Linux-specific and would be present in the Windows build too. It's very similar to this issue: https://itch.io/t/299710/bug-game-crashing-ayneris-sword-double-atk since the crash always happens at the very end of a battle. However, it happens regardless of weapon, even if nobody has a weapon that has a chance for a second attack.
I would guess the issue from the other thread is probably the same issue, and it's actually a UI drawing issue (i.e., trying to reference parts of the panel after it's been destroyed).