Unwelcome redirect on BackOffice Login

Environment:

Umbraco version: 17.0.0
Azure host application: https://blah-blah-blah.azurewebsites.net
Client qa host: https://qa.clientdomain.com
(Both domains point to the same application)
Front end service: Cloudflare

“UmbracoApplicationUrl”: “https://qa.clientdomain.com”
“BackOfficeHost”: “https://qa.clientdomain.com”

Website hostnames in CMS
https://qa.clientdomain.com/en   (english)
https://qa.clientdomain.com/de   (german)
https://blah-blah-blah.azurewebsites.net/en   (english)
https://blah-blah-blah.azurewebsites.net/de   (german)

Description of the issue:

Expected behavior:

BackOffice should Stay on “https://qa.clientdomain.com” after the login process

Steps to reproduce:

Run Umbraco ASP.NET site on azurewebsites.

Create Cloudflare route through to this site using a client subdomain

Set the settings in appsettings.json/CMS host names

Try to access the Umbraco BackOffice via https://qa.clientdomain.com

*** HugeDomains keeps rewriting this post WTF!

As an update to this - if we bind an external domain to the azure webapp in addition to the Cloudflare instance we are able to use the public domain to access the backoffice on that domain.