Thunderbolt add-in-cards tend to work best on motherboards that have either (a) a Thunderbolt header (labeled THB_C) or (b) an on-board Thunderbolt controller.
Reason: The firmware (BIOS) of a motherboard with either (a) or (b) contains support for Thunderbolt, including hot plug events, USB-C protocol, controller power gate functions, etc. We can even use an SSDT alone to activate Thunderbolt Bus for an Alpine Ridge controller.
However, the usual disclaimer applies:
Thunderbolt behavior, particularly with flashed controllers, exhibits idiosyncrasies that are unique to each board and each add-in-card and each version of motherboard BIOS (firmware).
The problems get worse the further back in time we go. Newer boards, particularly those with Thunderbolt headers or built-in controllers, perform the best (but still not perfect).
The Designare Z390 and Z490 Vision D with flashed on-board controllers have the fewest idiosyncrasies.
Have you considered upgrading just the motherboard to one that still supports your CPU, but contains a THB_C header?