Are you sure there are no privacy concerns with Root? Stoat seems to be better.
https://www.rootapp.com/privacy-policy
We collect the personal information and content of communications that you disclose through the Service. This may include messages, pictures and files shared between users and within communities. We may also collect voice, video or screensharing “calls” between users and within communities.
We may collect personal information concerning your interaction with the Site and/or App, including when you access the Site and/or App and your browsing activity on the Site and/or App (such as which pages you visit, in what order, and for how long). This may also include “traffic data” or tracking information provided by the Site’s host or similar providers (e.g., Google Analytics) that may be helpful for marketing purposes or for improving the Site and App.
Best to use open source chat with encryption support, I heard matrix is a somewhat popular choice.