I always though the approach of using SDR radios to provide entropy is interesting and relatively unknown: https://www.rtl-sdr.com/rtl-sdr-as-a-hardware-random

I always though the approach of using SDR radios to provide entropy is interesting and relatively unknown: https://www.rtl-sdr.com/rtl-sdr-as-a-hardware-random-number-generator-with-rtl_entropy/ https://www.rtl-sdr.com/rtl-sdr-as-a-hardware-random-number-... Disclaimer: I participated in the development of this.