I’d like to be able to chat from an Android phone without a SIM card.
Edit: Since several people have mentioned it, I’m including this note at the top. There are security issues with using a temporary number to register even if it is not needed to maintain the account. Anyone can gain access to the number and use it for account recovery, etc. I’m not an infosec person at all, but this seems pretty obviously bad. Some services will work fine with a landline or other permanent phone number, as long as you retain private access to the number.
If you feel like setting up a stun/turn server it’s possible to set up your own using something like xmpp or next cloud talk. Works for individual accounts with friends if not a plug and go app.
I have an ejabberd server setup for my family for this reason. Using the Conversations app off F-Droid and Gajim on desktops