Hi,
When I play a 4K video on my HTPC it plays fine on my UHD TV however in Kodi info bar it shows 480p instead of 4K!! from the resolution you can clearly see that it's playing in UHD.
my tv is UHD and in Libreelec setting the resolusion is set to 4K (3840x2160 @30Hz). When pressing the TV Info Button it show also 3840p 30Hz.
for info my HTPC setup is azrock z97e-itx/ac motherboard, 4G ram and I5 CPU (no graphic card)