The game can be run natively if you have a JRE installed on your system by changing the launch options to "java -jar game.jar # %command%"

It is easily possible to run this game natively, without using Wine/Proton, the developer should just add a built-in option to do so; without this, you are basically running a Windows JRE through Proton (can be compared to running Minecraft through Wine/Proton) and this may cause some problems (e.g. switching to another workspace caused the game to freeze for me)