A simple solution:
Buy an Intel N150 based NUC. Install LE 13 nightlies. That NUC has HDMI 2.1. Problems solved.
Older gen Intel devices often can’t communicate to HDMI 2.1 devices. Some have firmware update fixes. No chance of for old chipsets. Stop banging your head. Hardware refresh is a simple fix.
Additionally, I have a private build that supports multi-room streaming from a single N150, N250 NUC to multiple AVRs/4K TVs, tagless music/concert scanning with full metadata, no nfo Movie scanning (full metadata), DoVi,, Tidal Hi-Fi subscription play, Tablet based Remote app (user definable UI at run time), headless play of music, AVR control, TV control, special support for blu-ray audio discs and surround music,
Public release 1 July. NUCs, AMLogic, MacOs, Win, Android. *Forget AMLogic and Android for multi room support: Slow cpu, small ram, crap local storage speed, network too slow. Same with RPi. Old tech dump.