and I am an idiot/blind.
i missed the following section in the very well written instructions ( https://wiki.faforever.com/index.php?title=Setting_Up_FAF_Linux#Java_Downlord.27s_Client )
Copy the Steam RUN script
If you ran the game from Steam you should have a file called "run" in /tmp/proton_your_linux_username. The tmp directory is only temporary so copy this file to somewhere nice.
cp /tmp/proton_your_linux_username/run ~/Games/downlords-faf-client-1.2.0/
If you cannot find the run file, please check your Steam settings again. #Install the game, set launch options
Note: This file contains the environment variables for Proton that are necessary to launch the game in a Proton/Wine environment. It also contains the version of Proton that you have selected previously in Steam. The FAF client will use this file to launch the game after we set it.