Hi! Would you mind explaining why is difficult? Because on the Steam website (https://partner.steamgames.com/doc/steamdeck/proton) it looks like the process for the non-eos version is quite simple. You can't imagine how much I'd like to play HLL on Linux, it's the only game that holds me back on Windows today.
Ah, even the non EOS one is not that simple, especially with a older engine version or EAC. So for now reporting/requesting is key.