You might be interested in RadiaCode (full gamma spectrum) and RadiaCode Python Library - https://www.radiacode.com/ and https://github.com/cdump/radiacode

For Radon detection options are

* direct alpha detection via wet film + process (slow, and day turnover physical processing) OR optical scintillation of filtered air, or

* stochastic gamma detection via a full spectrum and a formula to identify and divide out main peaks and daughter peaks of overlapping common radiometric decay (Uranium, Potassium, Thorium) to guesstimate the radon