Exchange Server 2013 introduced modern public folders and also shift in the way clients access the public folders. Ever since, the Outlook for Mac client had limited or no support for public folders....
Updated Jul 01, 2019
Version 2.0
Blog Post
Supported Onpremise Exchange server versions for users that mailbox in Exchange Online doesn't have a native support for migration of the actual PF's to Exchange Online. If an Organization migrates PF's from their 'legacy' servers to EX13 or 16 to address the Outlook for Mac limitation, then they put themselves in a road block to migrate their PF's to Exchange Online (O365).