Flow may be used to sync a sharepoint contact list to users mailbox contact folder.
I think it would be a good idea to provide a template that does just that.
Sync a user selected contact list in exchange online with a user selected contact list in sharepoint online.
Either one-way or two-way.
A preconfigured template should be shared between users in a company so that activating the sync is very simple for new users.
Most users needing shared contact lists on the phone - in their mailbox for ActiveSync to sync it - would profit from such a solution. So the number of potential users is huge!