Don't even bother asking here. They will never tell you the truth which is that..
Screen mirroring no longer works with ANY roku TV.
The ONLY way to do it is to go into advanced settings and literally RESET THE NETWORK. And it'll turn your tv off and on. Do NOT put your wifi back on when the tv comes back on. The only way to screen mirror now is to do it without the wifi. And i don't mean just disconnect the tv from wifi. That won't work either. It only works when you reset the network and stay offline.
Idk what kind of bug this is or why they haven't fixed it. We got a samsung tv and surprise surprise, my phone screen shares just fine! And it's not just my android phone. It was an iphone. A motorola razr phone. A brand new samsung tablet. Laptops etc. And it's not my certain TV either. Cause we have two completely different brands of TV's. They just both happen to be Roku. Roku is more than aware of this They just don't care.