Seems strange indeed, I have a 2gb rx560 in mine and it works flawlessly with all three monitors I have connected. Have you tried turning on the screen or file sharing and seeing if you can log into the machine via those? Also what kind of connection used? Have you tried different cables or port used?Update: Just as I suspected, the Ethernet is working OOB! Thank you!
it is Realtek 8168, btw.
But I have another strange problem. Upon booting, there is black screen. I have to wait for it to go to sleep automatically, so that then I can wake it up, and then it works. After that, I can put it to sleep and wake up as many times as I want, and it never goes back to black screen. The only problem is the first boot.
The GPU in question is Radeon RX 580.