That seems to me the right kind of solution. Hardware devices from big companies are categorically untrustworthy, because of these companies' history of cooper

That seems to me the right kind of solution. Hardware devices from big companies are categorically untrustworthy, because of these companies' history of cooperating with surveillance, their incentives to sell out users, and the inability of users to verify what's going on in the devices. The answer is something that's verifiable - and that means precisely a no-code, low-tech source of entropy, plus a means of translating fluctuations into bits, the latter being "open" enough to enable users to confirm exactly what it does. And thanks, it's funny to think of putting a microphone in a colo server and using the roar of all the nearby fans and occasional voices as a source of random bits.