@BernhardRieder - The "Lighting Essential Concepts and Effects" course on:
https://learn.unrealengine.com/
… particularly the section of the class titled “Lighting Essentials: Reflections” helped me understand this quite a bit … like why your geometry is getting clipped in SSR. I agree with @rosegoldslugs that Planar Reflections are probably your best bet. You could also try experimenting with “Scene Capture Cube” … it’s explained in that same Reflections lesson I mentioned. Good luck!