SMS/RCS for friends/family in meatspace, Discord for friends in cyberspace.
Snapchat still seems to be a default conduit of communication for my family members and their respective friends. I do not have Snapchat and never will. They are mildly annoyed at my stubbornness.
I have yet to meet a single soul in my local circles who is willing to install any messaging platform over any concern of privacy or security. These are very simply not important factors to any of them. It’s upsetting. But, y’know, lead a horse to water, etc.
Discord continues to be a choice platform for my online friends circle. I don’t know so much about any of them, but I almost never use it for 1:1 private messaging. It’s there for the rare aside conversation. But its primary form of use for me is as a big town square in servers with dozens of people. It’s essentially my version of going to the mall after school or to the local pub after work.