Hi,
from what I know React Native can also target Universal Windows Platform (https://blogs.windows.com/buildingapps/2016/04/13/react-native-on-the-universal-windows-platform/#cdeqsd495HzxJZKP.97).
Have you considered to also target UWP in the near future, having mattermost native on windows phone and as windows 10 app will be really great.
BTW: Mattermost is a wonderful project, keep it up!
