Is it somehow possible to make an object invisible to an scene capture cube ?
I would like to know this as well, but I think it is not possible.
I found a kind of hacky solution for certain cases though.
You can use an if statement, in the shaders on the object you don’t want to reflect, on the camera view position.
For instance if you want to use the capture cube for a ground reflection you can do if cameraviewWS < 0 then set the mask of your shader to 0.
For this you also need to make the shaders, on the object you want to hide, a masked shader.
This could be a solution in some cases.