I have not. I actually don't want to experiment too much because I want to chat with other people, so popularity is really important to me. Session seems like it has a small user base. Telegram is the default in my local btc groups, which is a bummer. I may push people to move to signal. I've heard that Matrix.org is working on UX improvements to make things easier. If that turns out well then I might start pushing that.

I just looked at the google play store for download numbers:
Element: Over 500k downloads
Session: Over 1 million downloads
Signal: Over 100 million downloads

Signal absolutely DOMINATES.

Modus

Thanks for the rsponse. Have you guys tried Session yet?

jerry

bitcoin

What are some option to run private group chat?

Yes matrix is good. Signal is good too. Don't use Telegram. 

Matrix has more features but is a little more confusing to get started and stay secure. I like matrix because you can have a group with multiple channels (I forget what they call it). Multiple channels are great for groups, in my opinion.

Signal is easy for everyone to use, but you do have to tell people your phone number in order to chat with them.