A lot of spy cameras have an IR light that will be visible if viewed through your phone camera, so turning out the lights and doing a quick phone camera sweep can help.

I'm guessing this won't apply to all cameras though.

The popular in Korea anti-spy cameras/reflecting optical devices that find even pinhole camera lens. Something like this: https://www.amazon.com/dp/B0CQM298P6 But buy from somewhere other than Amazon. ;)

I saw an documentation about this some time ago, unfortunatley there is no reliable consumer method hat detects a well hidden non IR based camera.

it needs to draw power, so the ultimate way is to look for anything generating radio waves. there a few inductive methods to "listen" to electrical pulses near by, but you have to sweep every part of the room, take apart every source of EM. e.g.: light fixtures drawing power while turned off. same with wall sockets.

Explode a paint bomb in the center of the room that applies an even coat to everything. It’s the only way to be sure.

> I have yet to find a device or tool that would discover such hidden cameras.

eh?

IR based camera lens detectors are available for < £10

https://duckduckgo.com/?q=camera+detector&ia=shopping&iax=sh...