Some more data: It seems the issue is related to a bug on RenPy, which was fixed on 2022 https://github.com/renpy/renpy/issues/3978
But since the game uses an older version of the engine...
The issue can be worked around by playing on desktop mode (it only happens on game mode due to a conflict with gamescope)
another workaround might be to use the fix mentioned in this thread for another game (didn't test this):
https://steamcommunity.com/app/1609230/discussions/0/3488626756880789876/?ctp=2
proton 8.0x1 2024-04proton experimentalx1 2024-04
Compatibility Report
System Information
I confirm:
Symptoms
Game boots and you are able to interact with the main menu with no issues. Once the game starts, the app freezes up after a minute or two playing, with no option for recovery except exiting the app forcefully from the game mode overlay.
I tried with Proton 8.0 and proton experimental, and there wasn't any difference. I am not able to repro the issue on windows, which is the same build proton should be using.
Reproduction
-Open the game
-start a new game.
-play for around a minute or two (usually it happened to me when I reached either the second or third image.)