Also, I've seen numerous people working in the Quantum space claim that metastability is a quantum effect of ring oscillators, but very doubtful and the literature around it never mentions the q-word.
I also haven’t seen any oft-referred literature describing metastability do so using a quantum-physics context. The metastability itself is a product of quantum behavior but has been described well enough without needing it. Depending on what you’re exploiting randomness-wise (like the metastability or the oscillation period length), the type of physical description you use to analyze the noise source changes quite a bit. For most ring oscillator work, I prefer to look at the work near the 2000’s by Ali Hajimiri, none of which is in terms of quantum anything.