Azure AD Application Proxy now supports the Remote Desktop Services web client

Is the HTML5 Web Client supported with AAD Application Proxy in passthrough mode?

I currently have 2 proxy applications

• RDS Web Access - https://web
• RDS Gateway - https://web

Normal RDWeb works fine from both internal and external, however, HTML5 Web Client only works from internal.

If I choose in the HTML5 Web Client to download RDP files rather than launching them, it also works from external, but I can't launch apps directly in the browser from external.

The error comes right after the "Opening Ports" status and says unable to connect. Web client logs shows 3 errors.

• Exception: Possibly unhandled rejection: backdrop click Cause: undefined
• WebSocketTransport(ERR): WebSocket error received for url=wss://webapps.mycompany.com:443/remoteDesktopGateway?CorId=......... websockettransport.cpp(304): OnErrorFromJS()

• Connection(ERR): The connection generated an internal exception with disconnect code=ConnectionBroken(8), extended code=<null>, reason=WebSocket closed with code: 1006 reason:
  Thrown in thread 399652 at:
  websockettransport.cpp(335)
  Call Stack:
  at imb
  at fmb
  at Tp
  at Djd

  connection.cpp(1335): OnException()

Can anyone confirm if it is supposed to be working with passthrough or if Preauthentication on the AAD Proxy Application for the RDWeb is required?