The writing on the HDMI cable that came with my new Ultra 4850 says it is certified for 4K/60fps which I think would mean it's certified for HDMI 2.0.
HDMI 2.1 introduced support for 4K at 120 frames per second, 8K at 60 frames per second, and resolutions up to 10K.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X
