Multiplayer does not work out of the box and requires protontricks to install directplay. The used proton version (experimental of date 16.12.2021 and 6.3-8) protects files from being overwritten as protontricks attempts to install them, so i had to move the files:

directory: ~/.var/app/com.valvesoftware.Steam/.local/share/Steam/steamapps/compatdata/39190/pfx/dosdevices/c:/windows/syswow64/
files to move: dplayx.dll, dpnet.dll, dpnhpast.dll, dpnsvr.exe, dpwsockx.dll

Then installation of directplay succeeded

protontricks-flat 39190 directplay

And a langame was able to be hosted (before you were just thrown back in the menu) - to bypass the "disabled" in the mainmenu you can start the game with the startoptions "zonematch=true".

Don't alt-tab out of the window, you will have to restart the game.

Alt-Tab causes issues, you have to restart afterwards

Touch input coordinates not correct