Yes, my handwavy reading of the situation was that he left due to issues with zeromq that he couldn't/wasn't allowed 'fix'. Then Peter Hintjens unfortunately died a few years back. I haven't heard about nng, so thanks for that, I'll check it out.
ZeroMQ certainly isn't perfect, for example there's no way to tell if a message was successfully written to a PUB socket, or if it was dropped (just one minor issue)
https://stackoverflow.com/questions/13891682/detect-dropped-...
Anyway, This is digressing from the main topic