It is still an experimental version of the game, but I am happy to share with you that the Linux version of the game is available to be played for every Linux user.
You may need to transfer your save from your proton compatibility folder to this location: ~/.config/unity3d/HuardOuadi/Rogue Genesia/
If you encounter any issues, please report the issues in the game's discord: https://discord.gg/WbrgtCaP4T