[pclmulqdq]

One quick thing to add to this: /dev/urandom does not generate "true" random numbers. TRNGs generate 1 bit out per bit of entropy they collect from the environment, while /dev/urandom will not stop generating random bits when it runs out of entropy. That makes it a CSPRNG that is seeded by a TRNG.

For all practical purposes, a CSPRNG seeded by a TRNG is almost as good as a TRNG, but it isn't quite the same.

Linux used to recommend /dev/random which actually was a TRNG (although its entropy collection would sometimes overestimate how much entropy it got, particularly on servers), but it wasn't practical to use as your primary cryptographic RNG because it was very slow.

[SAI_Peregrinus]

A HWRNG is not necessarily a TRNG. As you say, a TRNG has one bit of entropy per bit of output. There's no way to prove this property is even possible in this physical universe, since it requires perfect unpredictability. Urandom is a CSPRNG seeded by a HWRNG.

[pclmulqdq]

This is true. The Intel HWRNG has actually been thought to be suspect in this regard in the past, although I don't think there's actual data about that.

Urandom also takes entropy from things like mouse movements, inter-onset intervals of key presses, and (on servers) hard drive seek times, so it actually does take in some of its own entropy in addition to that provided by the CPU.