Custom Company Holiday Calendar (New Outlook)

Is there a best practice to publish a company holiday calendar that can easily (or automatically) be added as an additional calendar for all users?  It's somewhat surprising that there's not a built-in method for an organization to publish an "official" calendar that's made available to everyone.

Is the best method for a user, say in HR, to create a personal calendar that's shared or published?  I think this PowerShell script (item #3) could then be used by an Exchange admin to automatically add that calendar to each user, individually.   Is that correct?

We have many users on the New Outlook but a fair amount who have not switched over yet.  I've searched for solutions, but many are for older versions on Outlook and I need to be sure they will work with the New Outlook.