Computer Configuration > Administrative Templates > Microsoft Edge - Default Settings (users can override)
Both
HKLM\Software\Policies\Microsoft\Edge\Recommended
Disables data synchronization in Microsoft Edge. This policy also prevents the sync consent prompt from appearing. This policy disables cloud synchronization only and has no impact on the 'RoamingProfileSupportEnabled' (Enable using roaming copies for Microsoft Edge profile data) policy. If you don't set this policy or apply it as recommended, users are able to turn sync on or off. If you apply this policy as mandatory, users won't be able to turn sync on.