I have a roku ultra hooked up to my vizio tv connected on a 4k 30hz port. It has 2.2 hdcp but roku ultra only detects it at 1080p resolution. I dont see the option for 4k 30 fps on the display settings.
I'm having the exact same issue. All of a sudden I no longer have a 4K 30fps option. Roku Auto detects only 1080p Dolby Vision HDCP 2.2. Playing Star Wars: Rise of Skywalker on Disney+ (4K) I checked System Information on my Vizio (while the movie was playing) and confirmed 1080p at 60fps. I can't even force the Roku to play any of the 4K options. Now it's playing everything in 1080.
Vizio Model: M50-E1 Version: 126.96.36.199-1
Roku Model: 4800X - Roku Ultra Version 10.5.0 Build 4201-C2