@ijatz_La_Hojita If your in doubt there are still some headsets with those old school mechanical kill switches or the shine bright new ones with touch button and bluetooth.
Cameras should have there own little brain and shine an LED whenever activated (at least external ones connected via USB).
On a mobile system with unknown hardware and closed source drivers your lost. Only way is to go for some open stuff like #pinephone or #librem5.
Edit: Forgot the 5 for mobile device by @purism