I've had a ticket open on this issue with Roku since October. It's now been six months, which I feel is more than generous. After being a Roku user and supporter for a very long time, I'm done. I'm not going to entertain the excuses, poor QA, or obvious problems any longer. I've been doing Pro AV product development for enough decades to know that when something doesn't fulfill its promise, it gets taken out and replaced.
I got an Apple TV 4K and it works perfectly & consistently with each & every app I use: Netflix, D+, Apple TV+, Prime, Hulu, P+, Vudu, HBO Max, Movies Anywhere, and the half dozen other apps I have. As a bonus, I can play and control Apple Music through the system without going through Bluetooth.
Going to put this 4800 on eBay. Maybe the next person will have better luck or will be happy with UHD/HDR10 and all the app inconsistencies. I will keep the Roku Express I have for travel since it seems they can manage 1080p.
My Ultra updated to 10.0.0 Build 4177-C2 from 9.4.1 Build 4237-C2 this evening. It's different - there's now a separate Display Type for 4K Dolby Vision TV but it only passes on the first two of the three tests. HDR10 still passes all three. For yucks, I accepted the two out of three DV setting and indeed it does not play DV content.
Seems like they know something's not right and had a go at fixing it but failed. Since I've been a Roku user for so long, I wanted to give them the benefit of the doubt and see what happened with OS 10. Perhaps they'll fix it someday. I'll never know because I'll be too busy watching Dolby Vision content on my new Apple TV 4K.
The 4K/HDR selectable options have been there since 10.0.0-4165 was released. 4177 is behaving the same as 4165 in terms of these new settings in my testing with my C7 (they all pass).
If your 4800 is connected to your newer LG, make sure you have HDMI Ultra HD Deep Color enabled for the port its connected to in the General settings for your LG - otherwise it will fail the (third) 60fps test.