Using a different setting, I managed to get it to at least correctly detect the name of my video card but there is still no acceleration and the VRAM is incorrectly detected as 7mb still. I've tried almost everything from inputting patched connectors hex to different framebuffers to injecting both nvidia AND ATI (even though I don't have an nvidia card lol) and nothing seems to work.
I also tried every Realtek 8168 kext out there and still nothing in that regard either.
You're probably just as confused as I am right now. If you know of any specific guide to try more complicated fixes, point me to it and I'll give it a try.
It seems that from reading around, 290s either just work or just don't at all with OS X and maybe I'm on the wrong end of that spectrum.
MoBo: Gigabyte GA-F2A88XM-D3H
RAM: Corsair 16 GB 1866 MHz DDR3
GPU: NVIDIA GeForce GT 730
DAC: FiiO E10K
OS: Apple macOS Mojave 10.14.6