As you aware the backup is managed by the cloud service, success and failure are handled by them, and there are currently no metrics/alert available. However, if you would like to test the backup, you can perform a restore to ensure its functionality.
If you believe this could be a feature request, you can share your feedback with the product team using the link below.
https://feedback.azure.com/d365community/forum/c5e32b97-ee24-ec11-b6e6-000d3a4f0da0
Hope this help! Let us know if you have any additional questions.
Thank you!