Same problem here . Detects HDCP 2.2 4K 60hz . TV diag shows input is only 1080p 60hz. This is the lates Roku Ultra purchased in Dec 2020.
Are you measuring that while on the Roku home screen? That screen is only 1080, perhaps it's resolution matching. Try it with a known 4K video playing. I admit that I've never heard of a Roku doing resolution matching like my Shield does, but maybe it's something they've added and didn't tell us.
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