Have you considered IRC? - Divisions by zero

Now you may be thinking; “That chat program is still around?” or “What the heck is a eye-arr-see?” Well let me tell you my friend. It stands for Internet Relay Chat and it’s been around for 34 years. It’s pretty much perfected at this point and quite easy to use if you have even the slightest technical knowledge. So IRC servers are separate from one another with each server having it’s own admins. Each server you connect to has it’s own bots ran by individuals to messages and ask for things. IRC servers work by sending slash commands much like discord does. To message another user you might type /msg coolboot2000 hello world! Piracy on IRC works by sending a bot a pm with the pack number you want. “Where do I find servers and bots and pack numbers?” It’s as easy as using a xdcc search engine. http://sunxdcc.com/ [http://sunxdcc.com/] has both a search and a list of networks. (DCC is Direct Client to Client meaning no files pass thru the server and XDCC is a version of DCC that allows large files to be transferred.) “How do I connect?” You use an IRC client with SSL support. mIRC for windows and Hexchat with a patch for Linux. Once installed you can use the slash command /connect or use the clients GUI buttons to make a connection to the server. “How do I make my own IRC client?” Follow the specifications here. https://en.wikipedia.org/wiki/List_of_Internet_Relay_Chat_commands [https://en.wikipedia.org/wiki/List_of_Internet_Relay_Chat_commands] There are a ton of pre-made IRC libraries for pretty much every programming language. Best luck friends!

To expand on this Have you considered Matrix? It's like IRC but encrypted AND includes a bridge to IRC so you can have the best of both worlds. https://matrix.org/ The most popular client here https://element.io/ though there are many others.
Matrix.org

Matrix, the open protocol for secure decentralised communications

Matrix is awful, sorry. I tried using it for like a year, but it kept randomly encrypting things and not letting ppl see messages, or worse, kicking them out of the chat