All games I try fail to launch when UMU is enabled.
I tried games from EGS (Barony), GOG (Brigador), as well as externally-added EXEs (Elona). All of them launch just fine without UMU, but fail when it's active. I'm attaching logs for all 3 (EGS seem to have different error from other two).
Running Heroic via flatpak on Fedora Linux, v2.19.1