I'm struggling to find it, but I read an article a few months ago where a team placed about 30 cameras hidden in a home and tried to find them all. Most methods found low single digits. Even the best ("an advanced lens detector" for $400) brought the total up to fewer than 20.
Really wish I could find that because now all I'm finding is dogshit articles claiming it's easy.
edit: found, it was from CNBC. https://www.cnbc.com/2024/01/22/how-to-find-a-hidden-camera-...
You can also check what devices are connected to the wifi but there's no guarantee they don't have a second network just for the cameras which you can't access.