The letter after the model number only indicates the sales chain - R = retail, RW = Walmart, X is anything else. You're Streambar will get it eventually. I have multiple Roku devices and none of them have been offered 10.5 so far.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.