Hell Let Loose EGS on Steam Deck won't progress past menu art

Trying to launch the free EGS copy of HLL on Deck via HGL. On Experimental it went straight to menu art with background noise plsying but progresses no further. With GE Proton it displays the UE5, Team17 logos etc then pans out to the menu art. This is the screen I'm on right now.

I've tried Proton Experiment, GE 9.2 & GE9.22, no change in either instance so far