You could use https://github.com/Kopano-dev/mattermost-plugin-kopanowebmeetings which offers integrated one to one calling, but as far as I know the Plugin framework is dedicated to the Web UI and therefore plugins are unavailable in the mobile UI.
You could use https://github.com/Kopano-dev/mattermost-plugin-kopanowebmeetings which offers integrated one to one calling, but as far as I know the Plugin framework is dedicated to the Web UI and therefore plugins are unavailable in the mobile UI.