Have you heard about a migration to modern public folders that has gone well? Apart that is from the demo migrations that appear at trade shows and conferences to show that all is well and that Microsoft hasn’t reneged on their promise to bring the cockroaches of Exchange kicking and screaming into the world of highly available mailboxes.
It was scheduled to be fixed in 15.20 but Outlook 15.20 was pushed back for QC.
You can revert to 15.8 or wait until Outlook 15.20.1 or 15.21 is released.
If so, and after the Exchange upgrade, you can reinstall Outlook 2016 for Windows.
Tip: If you have multiple Outlook email accounts, and one of the accounts (that isn't your primary account) is connected to an older Exchange server, you may want to remove it from Outlook to avoid these errors and use it with another email program, such as Windows Mail.
And the good news is that the procedure as laid down will faithfully attempt to migrate all the old, unwanted, unhappy, unreadable, and undesirable information from legacy public folders to their new homes.
That is, unless you take steps to stop this happening.
If they have a complaint about installing software outside of self service happy to roll them back to 15.18.
As per @Kaltsas said Microsoft has abandoned Public folders.
Public Folders(see screenshot) Nothing is displayed under the Root. I have confirmed i have access via windows Outlook 2010.