There is no official support AFAIK, but I wrote a plugin for it: GitHub - Rectus/UE4SteamVRPassthrough at ue5
It only provides the same projection the 2D Room View mode in SteamVR does, which at least on the Valve Index has a lot of issues. It does allow you to access the camera images inside materials though, if you need more access, you would need to modify the plugin.
I’ve also written a newer implementation as an OpenXR API layer. It doesn’t allow accessing the camera images, but it has much better projection. I haven’t seen any confirmation whether it works on the Vive Pro though. GitHub - Rectus/openxr-steamvr-passthrough: OpenXR API Layer for SteamVR camera passthrough