This article gives a general overview and glosses over some key areas
https://github.com/Azure/wordpress-linux-appservice/blob/main/WordPress/wordpress_migration_linux_appservices.md
Here is just one of the challenges I faced...
I deployed a new linux web app using managed identity. Didn't know how to access mysql for the new web app. After deleting and redeploying the site without managed identity, I found this article... wish I had found it before spending 3 weeks and 2 support tickets trying unsuccessfully to get help.
wordpress-linux-appservice/WordPress/wordpress_enable_managed_identity_with_mysql.md at main · Azure/wordpress-linux-appservice · GitHub