In today's update, the game receives full Linux support!
If you encounter any issues, you can try running it using Proton or revert to the older version running on Proton by right-clicking the Sister Ray icon in your Steam library and opening "Properties." Under "Game Versions & Betas," select the "before_linux_support" version.
The game can also now run on macOS (however, this version hasn't been fully tested, so official support hasn't yet been announced. It's not recommended for purchase without a Windows or Linux system). Please leave feedback on this version's performance in the Steam discussions.
If you encounter any bugs or issues, please report them in the Steam discussions so I can fix them!