I guess muting the volume of the microphone does act as a global microphone mute. You can also set a hotkey to mute in Settings>Keyboard Shortcuts under sound & media there is microphone mute/unmute.
For camera though there is no straight forward setting that I can find. On windows I had been using obs's virtual camera feature to stream a black a screen for my camera input. But on linux there seems to be no option for virtual camera in obs.
After some googling I came across this post. According to it sudo modprobe -r uvcvideo disables and sudo modprobe uvcvideo enables the camera. You could put that in a script file and run it whenever you want to disable/enable camera access. Or even you can add custom keyboard shortcuts for both in the settings app. Just make sure that in the command field you give pkexec instead of sudo for the commands.
Edit: It seems like I misunderstood the question a little. If you are looking for application-specific permissions like on android your best bet is to install those apps as flatpaks and you can configure their permissions in settings > Applications. I don't have any flatpaks that uses camera or mic so I can't test it now but if the app uses camera or microphone it probably will have a toggle for that.