First of all, ensure that the following remains exactly the same as in the original mattermost-mobile repo:
com.mattermost.rnbeta
.android/app/src/main/java/com/mattermost/rnbeta
.$ xcode-select --install
Fastlane is the easiest way to automate beta deployments and releases for your iOS and Android apps. 🚀 It handles all tedious tasks, like generating screenshots, dealing with code signing, and releasing your application.
# Using RubyGems
$ gem install fastlane -NV
# Alternatively using Hombrew
$ brew cask install fastlane
For more information you can visit the Fastlane docs.