My install went very well.
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One anomally I have found is it thinks my two DELL P2415Q monitors are 5120 x 2880 (5K/UHD+ - Ultra High Definition Plus) when they are only capable of 3840 x 2160!
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I removed Whatevergreen and lilu kext's and removed my frame buffer, video ports and de-selected Inject ATI and RadeonDeInit from config.plist.... all is well.
Sleep works, with the fans now ramping up for a few seconds, I can live with that!
iMessages and all the other goodies like AirDrop, AirPlay and Siri work well.
I'm getting a slightly higher GeekBench 4 score of 133039 (up from yesterdays score of 128739, so it might just be normal variation) and a Luxmark (v3.1) of 12347.
Blender is working well using the GPU, but as always it's around half the speed of the same benchmarks in Windows 10.

I believe this a Blender problem though.
Play's HEVC 4K films (Sony Camp 4K Demo.mp4) with very little CPU use... ~ 10% and VTDecoderXPCService ~ 4% .... butter smooth.
The only problem app I have identified is macXConverterPro... it crashes when trying to convert 4K videos to anything else... I'll start another thread for that though if I can't find the solution to the error it gives: "No device available for encoder (device type videotoolbox for codec h264_videotoolbox)"