Created attachment 145078 [details]
My RX 560 won't do 4k 60hz over HDMI. I have tested the cable/display with a different PC (that has a 1080Ti) and it works fine, so I can confirm that both the cable and the TV are capable of displaying a 4k 60hz signal. I have also tested with a monitor that is capable of doing 4k 60hz over HDMI.
xrandr only shows 30hz as an option on both the TV and the monitor.
Someone on IRC said I should mention I was able to achieve 4k 60hz with a DisplayPort cable to the monitor (sadly this doesn't get me 4k 60hz on my TV, which only has HDMI)
trek00 from IRC found this bug report: https://bugs.freedesktop.org/show_bug.cgi?id=104412#c14
which mentions running these commands, which seems to work and enable 4k60 over HDMI.
xrandr --newmode "mymode" 594 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync
xrandr --addmode HDMI-A-0 mymode
xrandr --output HDMI-A-0 --mode mymode
Created attachment 145079 [details]