Based on my research, the $30 cheap devices will not detect them. It is a scam. The only place an average person can get a real scanner is on eBay, and it will be $3k and up. The real scanners appear to be exclusive to certain types of organizations or state actors.
Maybe they have cameras inside your place. One thing is for sure: if they tell you there are, there isn’t. For example, they told me they had cameras in my fire alarms. So I would tell people, and I would look crazy. Because if there are, then people will demand to see the cameras. And it was hard to tell if there were actual cameras in them. And neither you nor the people you tell are going to spring $3k to prove there is a camera in the fire alarms.
They are using spyware tech undisclosed to the general public in combination with thermal imaging, and do not need a camera inside at all times.
If it is your apartment, they might have cameras. Because you will predictably be there. And it would be worth their investment in time and money. But if you find them, then plausible deniability goes out the window.
In public and private facilities, they likely do not. What is interesting is that there are gang stalkers who do not know either if there are cameras or not. And rather assumed there are cameras recording Targets 24/7.
One of my gstalkers got mad that I took a picture of them stalking me. And brought in another gstalker and asked them in front of me to show the stalking footage they have been collecting on me to prove that I had taken a picture of her. And the other gstalker said there are no hidden cameras inside the building, and therefore, there is no proof I took the picture.
On Quora: https://qr.ae/pCvNDd