Your options are CPU, Luoshuang GPU lightmass, and Unreal GPU lightmass.
Unreals GPU Lightmass is possible. Set all RayTraycing Effects to zero as the documentation says and when you play in VR switch back to DirectX11. The performance is good when you activate virtual texture streaming but you might experience texture popping when moving your head. You can deactivate virtual texture streaming to fix it, but then you might run into performance issues, depending on your scene.
Luoshuang GPU lightmass is still available even in 5.0 and is a solid option. I find it slower than Unreals GPU and it brought shadow issues for me with 5.0. With Unreals GPU Lightmass I find shadows are better and you can build bigger maps. But IF you have performance issues with Unreals GPU Lightmass then Luoshuangs lightmass is the way to go.
Never moved back to CPU.