Secret base on the dark side of the Moon,  last edited: Fri, 29 Sep 2017 11:37:07 -0500  
So I've had my XMPP server for awhile.  I did end up getting one of my daughters to use it, but her sister does not.  I'm assuming its because she has an iPhone, and the XMPP clients sort of suck for it.

Going to try another approach on getting them to use something other than FB Messenger.  This time with Matrix.  I have the server set up on my Cubieboard 2, just have to sort the NGINX reverse proxy.  With only a few people using it, I don't think it will eat too much RAM.
Matrix is great, I think it got a lot potential. I personal like the IRC bridge. The iOS client Riot works pretty well for me. Matrix is resources hungry, but not too bad, if you do not connect the big channels. I had a test server running in a VM (with 4GB) on my HPE ProLiant MicroServer Gen8, it worked fine. I hope you can convince your daughters to leave FB messenger.