I think I may be able to assist. If you are considering using macOS that is provided with your iMac (this is the same for the Mac Pro 2019 model), it's likely not to function as the software dependencies required to run the Oculus software are not provided for your operating system. If you consider using Boot Camp and running Microsoft Windows, then I would speculate it would function as any other endpoint with an AMD Vega GPU.
So I used bootcamp, (i had to upgrade to catalina first to get bootcamp to work) then downloaded the oculus app to my computer, hooked up an approved cable to my quest, and it worked like a charm. All of the older tutorials to set this up are before link-i have the entry level iMac pro and have played lone echo with no stutter or issue of any kind thus far. Also google earth VR is just remarkable. So it works, and I am EXTREMELY impressed with how easy it was, how my quest recognizes the link cable and takes me to the new interface. But yea use bootcamp. Better than going through any hoops to use OSX at this time.
This is working for me without issue despite the fact that I get a warning that it's unsupported. I have an iMac Pro with a 10 core Xeon proc, 64GB ram, and 16GB Radeon graphics card. Would love it if you guys would support MacOS natively so I didn't have to bootcamp but so far so good.