I've learned that the Mac (SMBIOS ?) model can be changed to one that does not have internal graphics, and then the external GPU will be used, and so problem solved.
I'd prefer not to change the Mac model, and instead want to use the solution provided by NoVPAJpeg.kext and, of course, Lilu.kext. I already use Lilu 1.3.6 (the latest release).
However... when I tried to use the latest release of NoVPAJpeg.kext - NoVPAJpeg-v1.0.0-built-with-Lilu-1.3.5-RELEASE.zip - my system crashed shortly after booting. I think this may perhaps be caused by the fact that NoVPAJpeg.kext was built with Lilu 1.3.5 and I am using Lilu 1.3.6.
MY REQUEST... can someone in the know please build a new release of NoVPAJpeg.kext, built against Lilu 1.3.6. This would bring things up to date, and hopefully solve the very irritating no JPEG decoding problem.
AMD Ryzen 7 2700X Processor with Wraith Prism LED Cooler
MSI Radeon RX 570 Armor MK2 8G OC Gaming
Corsair Vengeance LPX 32 GB (2 x 16 GB) 3200 MHz DDR4 DRAM
HP SSD EX920 M.2 1TB M.2 2280
Intel SSD 660p Series M.2 1.0 TB 80mm
EVGA SuperNOVA T2 1000w PSU
Corsair 750D full tower case