Quest Passthrough and URP

You do need to convert the passthrough shader on the standard pipeline to urp. 
There should be a couple of shaders that you can reference in oculus>sampleframework>usage>passthrough>materials. 

I had sucess enable passthrough in universal render pipeline.... didnt you use any special effect or renderfeature？You can creat an empty project with urp and test it.

You might find the answer on this post.

Maybe it is a little bit late, but I just want to leave a record, because I'm facing the same issue, when I add the URP as a Scriptable Render Pipeline (Project Settings > Graphics) I lose the capability of using "Underlay" passthrough..., it seems OVRPassthroughLayer isn't totally compatible for some reason. For my use case I found two options: (1) to use OVRCameraRig.OVRPassthroughLayer.Placement as "Overlay", setting the Opacity to 0.15 and making my objects glow to look like they are over the passthrough, and (2) using OVRCameraRig.OVRPassthroughLayer.Projection_Surface as "User defined", with Placement as "Overlay" and Opacity as 0.15 to display the passthrough in specific surfaces of my scene (right in front of the camera), and again making glow my objects to stand out the passthrough clearly. I decided to use the first option, at least until URP gets compatible with Oculus Integration passthrough options, or I find out that it is already a way to make this work.

Also, maybe it could be an option to change rendering pipeline (Unity Docs to Switch active render pipeline) when it is required passthrough, though it would be required having two versions of every material, texture, etc. and to disable URP features :(...