W.r.t. XMPP have you seen https://Conversations.im or https://dino.im? I'm using the former daily and the experience is very good, it's a modern messanger. Hangouts is stuck in the past.
I know Conversations, I like it but I lost all my Jabber contacts over the years (also due to the fact that the server I was using shut down). So, my list is empty. I have not tried Dino (I don't use Linux at the moment).