Same was fine till the recent launcher update, it does still show in the system monitor as org.chromium.Chromium on Native oddly.
But at the very least proton version seems to be fine for now.

I did a few tests and found five things which worked for me:

• add the launch option(so that the launcher uses xwayland instead of trying to use wayland directly)
  --ozone-platform=x11"
• start the launcher in a terminal from the folder where eu4 is installed with the command
  SteamAppId="236850" ./dowser
  (disables the steam overlay; might prevent achievements or multiplayer)
  
• open the compatibility tab in the eu4 properties in the steam library and check "Force the use of a specific Steam Play compatibility tool" and select "Legacy runtime 1.0". (I don't know if this causes any issues)
  
• bypass the launcher by changing the launch options of eu4 in steam to
  ./eu4 %command%
• use the windows version of the game with proton (though some launcher versions might not work in some proton versions and the performance is slightly lower and uninstalling the game will delete the virtual windows installation which proton uses and which contains the Documents folder with save games and other data)

Another options which I didn't test, but which probably will also work is to use x11 instead of wayland