Ubuntu 16.04 is going End Of Life at the end of April 2021, so without a paid-for subscription there won’t be any new security updates. We can use a couple of methods in PowerShell to list affected VMs in a tenancy.
When using an Azure WebApp (a.k.a. Application Service) behind an Application Gateway with the default document set correctly, visiting example.com/path/ works but example.com/path without the trailing slash brings up the blue 403 error.
If you take a Microsoft Azure course you may be given a limited-time Azure Subscription to help your learning. This post shows how to check the usage of that allowance so you can make the most of it before having to revert to your personal paid-for account.