I once read that noise of camera in total darkness is apparently a good source.

Speaking of ants, Fourmilab (i.e. John Walker, of Autodesk fame) used to provide a random number generator powered by background radiation: https://www.fourmilab.ch/hotbits/

https://www.random.org/ Uses atmospheric noise. These dudes use dice? https://youtube.com/shorts/ncoDq5EcPFg?si=lI6f9cw8dWcaDZ4Y

https://www.idquantique.com/random-number-generation/product...