After messing about and getting frustrated that my Samsung frame 2020 32" is not screen mirroring from my Samsung phone whilst my qe85r can....I have found a fix from a post online from 2018.
Go in to smartthings app and turn off auto updates. This is stupid and even 2 years later you have to do this just so the screen mirror works on the frame tvs. I didn't need to do this for the q85r 2019 tv.
Screenshot of the fix below from comment by someone who discovered it from 2 years ago.
