Some comments:
- Gigabyte B550 Vision D-P
- We experienced Thunderbolt connection problems in macOS that we were unable to solve.
- On-board Intel i225-V 2.5GbE Ethernet port has connection problems in macOS that we were unable to solve.
- ASRock X570 Taichi
- Thunderbolt add-in-cards such as GC-Titan Ridge encounter all sorts of connection problems.
- ASRock's DSDT/SSDT (ACPI) is the most non-standard and convoluted mess that I've come across. I cannot recommend any of ASRock's AMD motherboards (their Intel boards might be fine; I have no direct experience with them however).
I would therefore recommend one of Gigabyte's or Asus' AMD boards, but you'll be faced with the task of customizing the OpenCore EFI. The only tricky part is configuring the USB ports.
In the User Builds section, there is a guide for Gigabyte B550 AORUS Elite:
Leesureone's Build: Ryzen 7 3700 X - Gigabyte B550 Aorus Elite - RX 5600 XT 6GB https://www.tonymacx86.com/media/20200904_071220-jpg.192444/full Components Ryzen 7 3700 X https://www.amazon.com/dp/B07SXMZLPK Gigabyte B550 Aorus Elite https://www.amazon.com/dp/B089FT8G44 32GB G.Skill Ripjaws...
www.tonymacx86.com
One could add a Thunderbolt AIC to that system even though the board lacks a Thunderbolt header. Alternatively, you may want to consider the Intel-based Gigabyte Z490 Vision G. The Vision G is fully supported in my "Z490 Vision D" thread and it works quite will with a Thunderbolt add-in-card. Vision G has a Thunderbolt header. Intel Z490 boards might become extremely difficult to find soon, but the Vision G is currently available.