I couldn't change resolution any higher than full HD. System: Windows 10, Card: R9 380. TV: LG 55LA970W.
Could you please tell me when will you update the drivers to allow 4K. I assume this is a more general issue. There is an onlne patch: AMD/ATI Pixel Clock Patcher that allowed me to finally switch to 4K resolution on my LG TV.
Could you please check what the patch does and implement it in the next software release if it isn't harmful. It definitely helped me.