@Kobold Didn’t realise that nvidia drivers could be installed from flatpak.
Also didn’t realise that you had already experienced a near-exact occurrence of the same error last year, and that you had already posted about it.
If you had led with that, it would have saved some time.
If I were you, I would remove the flatpak nvidia driver, install linux612-nvidia / linux612-nvidia-open from the extra repo, install the game from the AUR as @Xephon suggested, fully configure the driver (early module loading, etc), and see if you still have issues.
Bonne soirée.