As Glenntech rightly says Google hasn't provided a way of disabling this and it is a handy feature for many and the only workaround I could find on my S21 Ultra is to pull down your features tray on your phone and scroll to the last page of these and hit the '+' button and draw down your hidden camera access and microphone access features to the last page of your features tray where they will become active and turn blue.. Turn the access features off and they go grey or whatever and you will never see the green dot again as total access to both your camera and microphone is denied, BUT every time you launch your camera or microphone in any capacity now you will have to give your phone permission to use it which I have tried and it rapidly becomes a pain. If you do ever find evidence of or even just suspect any rogue app of spying on you in any way though then following this procedure will stop it from doing so although uninstalling the app would be easier of course.. Disabling the camera and microphone overnight at least may be very preemptive if you do have security concerns...👍
