Unfortunately for some of them even if the game works there are often cases where either mods don’t work or some overlay/other additional software.
On your answer though, I was under the impression that when you configure the KVM passthrough setup it makes the video card you use for the passthrough inaccessible for the host itself and that to make it accessible, it requires undoing some of the config and a restart. Is this incorrect?
Were you using it on some other dudes junk by any chance or something…? Cuz otherwise that seems like a leap.