I was sort of able to get it to work with Ubuntu (14.04 Alpha), but not with dual monitors. I have a R7 250 card together with A10-7850k for multiple monitors. I was only able to install Ubuntu by disabling the integrated GPU in the BIOS and forcing the monitor on the discrete card, otherwise Live CD would start to flicker as soon as I clicked "Try Ubuntu".
With it installed, I switched to fglrx-updates driver. Rebooted and activated the integrated GPU. It found the second monitor but only at 640x480. After a second reboot it found the processor and identified the TV plugged to it. But that's with the monitor as a second desktop which is kinda useless (or how do I actually get windows into the other desktop?).
Problem comes when activating Xinerama. I tried all these drivers with these results:
fglrx-updates (dunno which version, from 2014/Feb/04): it wouldn't even boot.
13.30: would show Ubuntu loading screen and completely freeze there.
13.35 (zip is named 14.1 but file inside is 13.35?): would boot, show login screen, but it hangs after loggin in. Mouse still works, but it doesn't get to the actual OS.
Any tip on how to get this to work?
(PS: all this on a A88X-PRO motherboard, which I also had to update the BIOS driver to 0802 (latest as Feb/02) because it was giving disk and USB errors when trying to install OS' with MBR)