I am running a Roku TCL C167X on 9.4.2 build 4077-93 and airplay is set up and my MacBook is on Big Sur and my phones are all up to date. The airplay worked fine for the first 2 months but now the TV never shows up in the screen mirroring options. I see the device Roku (which is the tv) but not Living Room which is what the TV is setup as in airplay. When I try connecting to Roku nothing happens.
See this longer thread. Roku has not acknowledged a problem exists. It took months just for Roku to ask for more information. The last post (yesterday) says the problem (which seems to have been due to the last untested software update) was fixed for someone. Maybe a new update is occurring. As usual, Roku hasn't explained anything about that, what to expect (or, that there's even a problem).
"People are often amazed at how much we’ve done with the number of engineers we’ve got." (Roku CEO Anthony Wood, Austin Statesman, Oct 4, 2019). "Amazed" is one way of putting it.