5.5 release notes even mention SM5 Lumen support.
Nah we have it running on APUs and really cheap non HWRT pixel streaming machines from 5.1 - 5.4
its literally the way to get performant GI in UE5 (GTX 1070 my guy … not even RTX)
I track source changes and I’m almost for certain the Fortnite and UEFN DX12 requirement likely got pushed into UE5.5 main and it was an unintended side affect.
Wouldn’t be the first time I’ve seen this.