By Designare I believe you mean the X299X Designare 10G and not the X299 Designare EX since only the former has 10G LAN, correct?
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As far as I know, MacOS supports Aquantia AQC-107s 10G LAN (the iMac Pro has Aquantia 10G LAN and so does the Mac mini 2018 when configured to have 10G LAN), but I am not sure if the Intel 10G LAN ports on the X299X Designare 10G are supported.
The ASRock X299 Creator apparently has a 10G LAN based on Aquantia AQC-107 which may require a kext patch for it to work with MacOS :
Starting with macOS High Sierra 10.13.2 there is an included driver for Aquantia AQtion AQC-107s based 10GbE network cards. Others like AQC-107, AQN-107, etc require a kext patch. Performance is identical between them all. Compatible cards as long as they have AQC-107 chipset: Syba 10 Gbe https:/...
www.insanelymac.com
If the motherboard has Thunderbolt 3, something like this can work to add a 10G LAN port via Thunderbolt 3 :
10GbE Thunderbolt adapter with NBASE-T support. Connects through a RJ45 10GbE port to 10GBASE-T 10GbE networks. For Thunderbolt 4 and 3 computers.
www.sonnettech.com