XR11 remote won't work with Amazon Omni Fire TV 65"

I bought this TV: https://www.amazon.com/amazon-fire-tv-65-inch-omni-series-4k-smart-tv/dp/B08T6J1HG8

My Xfinity XR11 remote won't work with this TV. When I go to the menu to pair the remote and it lists the hundreds of brands of TVs, Amazon isn't in the list.

I found this thread on the Xfinity forums where other people were having problems getting their remote to work with their Amazon TVs of various types. I tried every single remote code in that thread, it still doesn't work.

I tried the setup - 991 - channel button method. Still doesn't work.

With some of those codes and with the 991 method the remote would control the volume. One or two of them had the power button able to turn the TV off, but it wouldn't turn it back on. (I tried both the TV and All Power buttons on the remote each time).

Is there anything left to try? Should I spend an hour on the phone with Xfinity support, would they have any more information? Should I contact Amazon about this?

Would it be possible to request to have my XR11 replaced with an XR15, maybe a newer model of remote would work?

This TV is for my parents and it's kind of inconvenient for them to have to use the second remote that came with the TV just to turn it on every time they want to use it, then go back to the Xfinity remote to control the cable box.