Whether they can legally, whether they need to, whether they wish to, whether they even have the time... are all different from whether they can technically.
Anyone can only "see" you visually in your home can only do so IF you have an Internet camera in the room, and leave it switched on.
Aural eavesdropping is perhaps a biggwer problem, as devices like 'Alexa' are designed to do that, not for Police use but so companies like Google and Microsoft can tell their advertising-agency clients about you.
Simple solution: don't buy any such instrument; but if you must, switch it off unless and until you really "need" use it for your purposes!
Eelectromagnetic ("radio") eavesdropping can only work from electrical impulse signals carried by metal wires. The power hence radiation range is low. Fibre-optic services cannot radiate anything because the data are as pulses of light, not electricity.
If you worry about wireless devices within your home... don't use them.
(My only wireless "appliances" are a central-heating thermostat, door-chime and utility "smart"-meters. My portable telephone happens to be in another room and switched off as I type this, and is not linked to the Internet anyway.
I do have a radio car-key: needless pseudo-sophistication whose latest types for the most expensive cars are absurdly insecure against car-theft gangs. Still, it only transmits when you press the button, and my car is of too little value for such gangs anyway.)
