Well, I started this in 2017 and the first public release was in 2018, so it's been around for quite a while and also predates Andreas video.
Furthermore, it is not meant (just) for messaging, one of our example apps was indeed a messenger but the firmware itself just gives easy ways to send and receive data. We wanted to keep any application logic out of the firmware to make it general purpose (and maintainable).
None of them has achieved critical mass, and none of them will if everyone interested in the subject insists on making their own.
Andreas Spiess covers several mesh networking/messaging systems here:
https://www.youtube.com/watch?v=TY6m6fS8bxU