I want to create a multimonitor system connecting 5-12 monitors in Ubuntu 18.04 as my personal workstation. My plan is to buy several cheap pcie graphic cards on ebay, putting them into a system with three pcie x16 slots. I don't need much gpu power since this is not a gaming/cad system but one to work/surf. I am eyeing for several old HD 5870s (1x DVI, 1x HDMI, 2x Mini Displayport), connecting them via adapters to VGA/DVI capable monitors. I have trouble finding any recent information on the internet if this still works in 2018 with the amdgpu driver on Ubuntu 18.04. I don't want to buy before I am sure it works. One card alone is sure to work from what I can gather, but two and especially even three together?
Hence my question: Are several old radeons (5870s for example) on an amdgpu driver for multimonitor still supported on Ubuntu 18.04? Does anyone have such a configuration running on Ubuntu 18.04? What configuration worked for you? I know that the newer cards work even better, but cheap is what I am going for. I know that old nvidias work with multiple cards by experience, but radeons?
Possible configuration I thought of for my case:
3x Radeon 5870s (=3 cards * 4 outputs = 12 monitors)
Asus Crosshair IV mainboard (three pcie x16 slots)
Old 19" Monitors with DVI/VGA, all of the same model/type
Would be very thankful for any answers,