Discovered same problem like you with the HDMI-connections, as my LG UHD player does support Dolby Vision.
My current work around is to manually connect either LG or Apple TV to HDMI
Hi Kiwi4all
Since you do have 2 sources capable of Dolby Vision (LG UHD Player and Apple TV), the only work around will be to use a HDMI Switcher which can take in 2 UHD signals and then connect to Loewe HDMI 4.
Before your post on HDMI 2.0 ports on Loewe, I had already found and ordered an HDMI Switcher which I think is the best in the field. The link to the product is here in case you end up using Both, LG UHD and Apple TV 4H HDR and feel the need. Since I have the Sony UBX 800 which can only play HDR (No Dolby Vision), I am just plugging it to HDMI 2 on Loewe and Apple TV is on HDMI 4. Fantastic picture quality though even with just HDR via Sony.
http://www.gefen.com/product/4k-ultra-hd-600-mhz-4x1-switcher-EXT-UHD600-41