Retire last Exchange Server but keep directory sync

Hello all --

I'm looking for guidance on the recommended way to retire our last Exchange 2019 server while maintaining directory synchronization in our environment.  We do not have any mail flowing through our exchange server, never have. It was only installed 10 years ago for a hybrid deployment.  I believe one supported path is to stand up a member server and install the Exchange Management Tools on it.  Given that Exchange 2019 is already out of support, is the the long term path moving forward?  

I've also read about an attribute "IsExchangeCloudManaged".  In this scenario, I can set this on a per-mailbox basis and manage attributes such as proxyaddresses, extension attributes, and other non-AD-managed attributes.  Is this the more forward path to take?

Thinking about our user provisioning process now, we have a PowerShell script that creates the user in AD and connects to our hybrid Exchange server to Enable-RemoteMailbox.  In this scenario, we would still create the user in AD, wait for the sync to happen, then enable the IsExchangeCloudManaged.  Would this now provide the ability to manage additional addresses, or even, shared mailboxes without having to migrate from AD --> EXO - all while keeping AD in sync with cloud mailboxes?  Am I thinking about this correctly?

Thanks for any insight

sb