From the latest lodestone notes:

Additionally, once the account link has been performed, users will need to utilize the new launcher layout introduced with Patch 6.0. If using the “Original Launcher Layout” setting in the launcher Config menu, please switch to the “New Launcher Layout.”
This will lock out anyone using Linux or who were planning on using the Steamdeck to play the game.

The new launcher does not work with proton.
The old launcher works fine and allows Linux users to log in and then they can get the game running fine.

Can this be changed or do we need to downgrade this game on the Proton ranking page?