I don't think azure-docs repo is the right place to ask for help/suggestions as maintainers are not very responsive because their sole job is to push internal docs to public docs. But I understand your frustration.

However, I believe you could have set up "public IP prefix" using azure cli. I do not think you needs a azure managed firewall.

Adding managed firewall just to have edge IP is like saying I want to add a outside patio to my house, sure let's add a security check point for the neighborhood first.