You can try using an Android device (though you’ll need a domain name for your router for DoH to work) if it’s running Android 9 or later - it has an option called “Private DNS” under Connectivity/Connection settings. Entering your domain name there (as long as it points to the device running AGH, and port 853 is accessible) should result in no error messages (otherwise after saving the settings, the menu option will display “Couldn’t connect” instead of the DoH URL).
Then you can check both the AGH logs and the on-screen information of the Android device to verify it’s working.