I'm pretty sure the British TV license says otherwise, although in practice it's an often abused extortion mechanism. It's quite possible to detect dedicated tuned receivers as well.

In fact, in many countries pointing your SDR at 2G/3G/4G/5G frequencies is basically an instant felony, even without attempts to decrypt the traffic. If you get caught watching such traffic, you'll pay much more than just a small tax.

As if there's no way to codify that a device determining a spacetime location from GPS signals is a taxed good.

To give another example, you used not to have to pay public broadcasting tax in Germany if you didn't have a TV or radio in your household. I would be highly amused to see you try to argue "it's just an electromagnetic radiation plotter, what do you mean tele, eh, vision?" to an unamused government official.