Ah, great.
Well, I recently bough a Mac Pro 2010 for peanuts, and have been messing with it.
It had a Radeon HD 5770, and I always intended on upgrading that.
As well as make it possible to boot with an NVMI SSD.
And probably run Catalina.
I didn't realise it would need a Metal capable GPU to go past High Sierra, though.
Not a big deal, although for some things it's a hassle.
In any case, can run > High Sierra as VM: I already do that on a MacBook 2012.
I wish there was a bigger list of GPU's that run Metal.
The Apple one is quite small: there must be others.
There is a list of Metal benchmarks from GeekBench:
Geekbench Metal Benchmarks
From other forums, I know that the Titan Xp is Metal capable, although not on Apple's list.
And the GTX 1080 Ti is on Geekbench's list.
But all the faster ones are Radeon.
I'm not a gamer, but want to use the upgraded MacPro for a workstation.
And I need CUDA capability, so it means AMD is not an option.
Maybe the work around is having a cheaper GPU that is Metal capable (to run > High Sierra), and have a 2nd GPU that my number cruncher.
You can get an older Tesla that's pretty good for HPS, and inexpensive.
But that's assuming whatevver software I'm running for it can use the GPU it needs.