I tried with Proton Experimental, Hotfix, and v9 using steam; steam-runtime; and steam-native; and all failed similarly. There isn't much output, but I do see "ERROR: ld.so: object '/home/lmat/.local/share/Steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored." each time.