What chat services can I use?
Chat services work inside Messaging. They have no icons of their own in the Launcher: you add an account, and your chats appear in Messaging alongside your other conversations.
Once an account is set up, you use it as you do any IM account (learn how). To remove one, see Delete an IM account.
Telegram, WhatsApp, and Teams can also make voice calls (learn how).
Checked against the LuneOS code and installed apps. Nobody has tried these steps by hand yet, so tell us if something differs.