UHD722 for the best soundquality and best convenience from ATV4K.
HD621 if keeping it in 1080p.
HDMI audio extractor, don’t know if they have 3-4 SPDIF out? Otherwise they can’t keep things lossless. ATV4K outputs multichannel PCM over HDMI.
Optical output from TV, convenient but lossy in multichannel probably not bitperfect. Might be multiple conversions.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.