I'm mildly disappointed that banana is not listed as option for test material

Even though bananas are famously radioactive, it's very low activity and I don't know that a regular detector could pick up the emissions from a single banana. You'd probably need a truck full of them.

For those curious about the radioactivity of bananas. https://what-if-origin.sciesnet.net/158/

haha, yes... unfortunately they emit such an extremely tiny amount you can't measure it with ordinary means, I tried:

https://twitter.com/BetterGeiger/status/1523769482602196992