I can tell you some things that will scare the shit out of you desu.
Commercial WiFi routers can be used like radar to see who is where inside of a building. This was proven by a university research team quite recently.
The new 5G cell nodes that are being installed every few blocks all over North America are going to have this same ability, but on steroids. They will be able to see a three dimensional map of the inside of every building in the area, and the location of all people inside of the buildings.
Exactly like in the Batman movie The Dark Knight when Batman had Wayne Enterprises bought up a bunch of cell phone companies so he could install some tech that would allow him to have three dimensional x-ray vision based on the radio signals being emitted from people's cellphones.
Internet of Things:
Internet of things devices, any appliance or device you connect to your WiFi at home (TVs, fridge, thermostat, whatever the hell they decide to stick a WiFi antenna into next) can and probably are spying on you. If the have a microphone in them, they are listening to you. If they don't have a microphone, they probably do have one anyways (they can be hidden inside chips on the mainboard).
If they don't have a microphone, the data they gather about their usage can be polled into massive databases (this information, tons of it, is fed into AI and used to make predictions about world events. Yes, knowing if someone is currently using an appliance in their home is valid and useful data, once you have that information for hundreds of millions of people).
If it doesn't have an explicit backdoor, it will eventually have a vulnerability discovered that can be exploited, turning it into a spy device. Device / appliance manufacturers very rarely update the firmware on their devices for longer than a year after they sell a product, if they ever do at all. Not to mention that few people bother doing the firmware updates.