This is an interesting thread. I'm a fairly new user to ubports and really liked it. Unfortunately I cannot flash it to family members, because there are missing apps and I did not find voice guide for the map in the language I was looking for. One of the missing apps was Jami.
I respect Thatoo's opinion but I have to say I do not share it. I'm not sure that an app is bad in itself just because someone did not hear about it. Btw it's called Jami, not Jamie. And for me it's great as I tested with contacts and family members on Android, iPhone, Linux and BSD.
I'm not trying to say that Matrix is bad, because I used that too and it was ok for me. I just liked Jami better. Also I read about privacy issues regarding Matrix. I also tested Xmpp (which was ok, but some features were missing) but Jami is just easier to use. Also, I would not call such a cross-plattform app isolated, but I know what is meant above with the bridges. Anyhow, all I'm trying to say is that for some Matrix might be preferable, but for me (and surely for some other users) Jami is a great messenger and it'd be great to see it on ubports too.