Microsoft has been pushing ‘Add to Onedrive’ over ‘Synchronize’ for a while now. I missed the enhancement from 500k to 1000k max items.
This makes a lot more viable!
Ensuring users don’t sync is easy with the HideSyncButtonOnTeamSite parameter of Set-SPOTenant, but that does not invalidate existing sync relationships.
So how do we detect which users are syncing, and which libraries? Because we want to transition them too, right?
Here’s a nice remediation script to throw into Intune that’ll help you do just that!

download/readme: https://github.com/jflieben/assortedFunctionsV2/tree/main/O4B/Unsync