The answer to your question is that now Airplay will not become available unless there is a device available to Airplay to.
If you go to System preferences and type Airplay into the search box you will get a list of preferences. At the bottom of that list will be, "show screen mirroring status in the Menu Bar' Click that and you will be taken to Dock and Menu Bar preferences. Tick the box that says, Show in Menu Bar and if you like select "Always" from the drop down menu below.
Now you will have the Mirroring icon on your Menu Bar but, unless there is a compatible device to mirror to you will not see any device options when you click on the icon.
The way it works now for me is when I am home in Australia I have an Apple TV and that causes the Mirroring icon to appear on my Menu Bar, I don't need to have it set to "Always", I have mine set to "When Active", it just appears when the Apple TV in within range of my M1 MBP on the same WiFi network.
If you do not see your smart TV in the mirroring options then it is not available for some reason, eg compatibility or settings.
Check your TV settings, manual or website for Airplay setup.