We use Ruby and Ruby On Rails for most of our projects. However, when it is not enough - when we need really high perfomance - we add Go to the mix.
Though we use conventional Swift for iOS development and Java for Android development, we also can use Xamarin and Ionic if it suits best for your project.
We are using Docker for containerization, Amazon Web services as a platform and Ansible to automate infrastracture management.
He creates user-friendly UIs and draws stunning graphics. Check his works at aceed.ru.
Mostly back end developer on Ruby or Go, but no problem in use Angular or React for front end. There is his website.
Despite the fact that he uses Ruby to do his tasks, he is our Elixir evangelist. Also use Angular or React in his work.
Our front end wizard. Uses React.js and Node.js as his designated weapon. Check his github account.