Is it possible for when there is a Pull request being completed, it creates a custom app_offline.htm file, and then removes it once the request completes/fails afterwards?
Been left with a white screen for users when the pull request is being actioned isn't ideal and would like to automate it as much as possible.
For this issue , I am afraid it is currently not supported in azure devops. The UI in azure devops are as designed. You also can't add a custom app_offline.htm file to the root directory of azure devops.
If you want an ideal display page , you could add your request for this feature on our UserVoice site, which is our main forum for product suggestions. Our PM and product team will kindly review your suggestion.