You could bring it to a large festival or even a protest. Law enforcement deploys them all the time. I found one using SnoopSnitch on an Android phone while at a large festival here in Louisiana.

Does that work by comparing known cell sites to found cells sites? I know some StingRay detectors use that method and it's prone to false positives around large events where mobile carriers or 3rd parties bring in legitimate temporary cell sites to improve cell service at the venue and provide more capacity.

Visit Washington, DC.

They are quite common in some municipalities. There are folks who talk about this at length in cybersecurity circles every year at conferences, it’s been an issue for a long while and the scope of the problem continues to grow.

The EFF also writes in the topic from time to time. See: https://www.eff.org/deeplinks/2024/06/next-generation-cell-s...

Is it possible to detect these using SDR networks?

https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-f...

I have no idea. I'm not an RF expert, but I'll ask this the next time I run into one. Great question!

Here in Brazil criminals are starting to use those to send phishing SMS, exploiting our ubiquitous mobile payment system (pix) or pretending to be a second authentication factor for banks.