According to Sony, all the HDMI ports should do it - as long as you've activated Enhanced format:
https://www.sony.co.uk/electronics/s...icles/00167580
EDIT: Sony's content is confusing - for 4K 60fps (which is what the iPlayer content is), then yes it's HDMI 2 or 3:
https://www.sony.co.uk/electronics/s...icles/00167110