having same issue.... did you get it resolved???????

having same issues. it will show my screensaver and I can hear what I want to mirror... but it is not mirroring

its not apple tv its got to be bigsur.... my iphone will mirror but my macbook air will only show my screensaver and I can hear what I am trying to mirror but not see it. very frustrating. you cannot not get any help from Apple... had trouble with Apple music family sharing for years.... still not resolved