--I am still working with your SSDT for enabling my GC-Alpine Ridge (unfleshed).
after much experimentation, I generally get one of three conditions after a boot.
1) Apple TB display shows the entire boot, and at the end of boot the display functions but not the peripherals (camera, mic, display audio out).
2) Apple TB display shows the first part of the boot, then goes dark for the rest of the boot. at the end of boot, my secondary display (connected via DVI from RX590) lights up. in system information, "no thunderbolt devices".
3) boot as in #2. at end of boot, TB display not lit up, but secondary display shows full TB tree in system information, and peripherals work.
and very rarely: apple TB display shows full boot sequence, and lights up at end of boot with peripherals working.
I have not been able to achieve situation 4 in a while. attached are system info screen shots and IOReg for situation 3.
my DSDT has the XE17 rename but not the XINI rename.
thanks for your help!
edit: random thought. remembering back to the "rehabman days" of laptop hacking, he was a strong proponent of setting the load order of ssdt's via clover. I'm wondering if the randomness of my situation has to do with different load orders of SSDT-DTGP.aml and SSDT-TbtOnPch-Gigabyte-Z390-AORUS.aml? the only other SSDTs in my ACPI/Patched are SSDT-UIAC and SSDT-nvram.