I don't have a UHD722, but I have a similar problem: getting 18Gb 4k to my TV, while getting audio somewhere else. I purchased an HDMI 2.0 18Gb EDID audio splitter box. 4k goes to TV, audio goes to Oppo203 HDMI In.

Box reports 7.1 LPCM to connected devices, via an HDMI2.0 switch before the audio splitter, and that selects between PS4 Pro, Roku and Mac.

Input selection handled by Harmony remote. The audio out could just as easily go to a HD621 for a 562 or 861.

Cave: Trinnov Altitude CI-8; Oppo 203 Vanity HD; 6xDSP5k, DSP5kC, D1500; Sony Z9D, PS5 Pro; Apple TV 4K
Living: Wiim Pro; Rega Planar 1+; 2xDSP5k
Master: Wiim Pro; 2xDSP3100
Kitchen: Bluesound Flex stereo pair / Amazon Echo Studio
Deck: Wiim Mini; Random Chinese Class D; Cambridge Soundworks Outdoor 52s; Polk Sub;
Garage: Wiim Pro; 2x5k