Sorry: while definitely broken in 91.12.0 ESR, it indeed works for me too in 103.0.2 on FreeBSD. I probably forgot to set
hw.snd.latency_profile=1 before testing with latest Firefox yesterday; I usually use the lowest latency setting possible although it breaks recording, because I much more often play with software synthesisers than I use my microphone!
I once chose the ESR version of Firefox for my laptop (which I don't use on a daily basis), thinking it would be less prone to issues than the fast changing regular release. Well... not always that way, it seems.
Still interested to know if progress was made on the NetBSD issue.