I may, most likely, be overcomplicating this / missing something - soz in advance if so…

I’ve got a scene that is a plane with Y = 0 - it’s the “ground”

I want to find out what the X + Z are when the user clicks on the screen for my ground plane (no hit or co-ordinates)

We’ve got PositionToWorldPlane, I guess that’s almost what I need apart from using YPlane rather than ZPlane.

PositionToUpPlane would tell me where a ray from camera intersects YPlane giving me (X, YPlane, Z) - YPlane = 0 being the most interesting of course.

The ground plane may have a transform (most likely) but I know those so applying the inverse transform to (X, YPlane, Z) should now tell me where on the grid, if at all, my mouse click was.