It should be noted that while the article recommends TRNGs with radioactive substances, those are completely unnecessary. Any high-gain electronic amplifier wh

It should be noted that while the article recommends TRNGs with radioactive substances, those are completely unnecessary. Any high-gain electronic amplifier whose input is connected to a resistor, or for a higher signal level, to a diode, will produce copious amounts of random noise at its output. If the output is converted with a comparator to digital, you have a good source of random bits. Older people can remember the random audio or video noise of ancient radio receivers or TV sets, when they were tuned outside a correct channel. In the past, there were easily available analog TV tuners for PCs, which could be used as noise sources. Nowadays, it is still possible to use the microphone input of a PC and connect to it an external analog noise source with a negligible cost, made on a little PCB with a small amplifier IC, e.g. an operational amplifier or an audio amplifier. The microphone input of PCs provides a weak 5 V supply, which would be enough to power a noise source. The only problem that exists with any analog noise source is that the imperfections of analog-to-digital conversion, e.g. the fluctuations of comparator thresholds, due to temperature or age, can cause a bias in the random bits, so they do not have a truly uniform distribution. This problem also exists with radioactive sources. Thus the bits must be processed to remove any bias. There are more sophisticated methods, but even the brute force method of using a one-way hash function, e.g. one of the SHA-3 or SHA-2 variants, to hash the bits and produce a uniform random number, is good enough. Most modern CPUs, since Intel Ivy Lake, have instructions for providing true random numbers. However those are less useful outside their main intended application, of providing temporary session keys for TLS or other network protocols. Some CPUs, especially from AMD, had bugs in their RNG, so they provided bad values. Even where the TRNG is good, the output passes through AES-128. Its state is small so you may encounter the problems mentioned in the parent article, of unreachable parts of the solution space that you are investigating in some Monte Carlo simulation. It is preferable to be able to choose yourself the bias-removing method, to be able to use a hashing method with a much greater state.