UPDATE 13/08
You can sign in to the Citrix TechPreview (scheduled for Q4 and GA 2017) here https://www.citrix.com/global-partners/microsoft/remote-app.html
Microsoft has announced the retirement of the Azure Remote App solution.
Azure RemoteApp was the ability to publish applications and resources using Remote Desktop technology through Azure, either in full cloud mode (ie application and applications/resources hosted on Azure) or in hybrid mode (ie using Azure to access applications/resources hosted either in Azure or On Premises).
The Azure RemoteApp is not anymore available for sale and if you are already using it, you can still continue to use it for one more year while you look for alternative solutions.
See https://blogs.technet.microsoft.com/enterprisemobility/2016/08/12/application-remoting-and-the-cloud/ for the official announcement and alternative solutions.