I have been building a lot of my open source projects with Azure DevOps (AzD). Now that we have YAML build support I have been converting my projects to YAML builds. When you use the graphical editor you can find the status badges for your readme files on the "Options" tab.
However, when you use YAML the graphical UI is not displayed by default when you edit your build. Instead you are simply shown the contents of your YAML file.
Using the ellipses you can return to the graphical editor by selecting "Pipeline settings".
Unfortunately, the "Options" tab is missing on YAML builds.
So where are you supposed to get your status badges? You can find them on the "Builds" page under "Pipelines".
Now click the ellipses next to the "Edit" and "Queue" buttons in the upper right hand corner. From the menu select "Status badge".
Selecting this menu item will display your status badges.