The major messaging (and notification, if you believe the rumours) networks are all based on xmpp.
The issues are basically: big vendors want lock-in so they disable federation and spam. I remember seeing an XEP that aimed to solve the spam issue for federated xmpp.
Matrix - Works well, but UX is too techy for my non technical friends.
IRCv3 - never tried.
Currently, I am using Tox P2P, so far it's working best.
I am looking for a web client because native clients don't provide me Telegram like feel.
So, if I find some time, I'll be writing my own web front end.
I am also looking to hire people to work on my Tox web p2p frontend.