Put:
{ "SyncDisabled": true, "RestrictSigninToPattern": ".*@example.com" }
and place in the following location:
Chrome: /etc/opt/chrome/policies/managed/disable_sync.json
Chromium: /etc/chromium-browser/policies/managed/disable_sync.json
Chromium kept signing me into my Google account.
Put:
in a file called disable_sync.json (for example)and place in the following location:
Chrome: /etc/opt/chrome/policies/managed/disable_sync.json
Chromium: /etc/chromium-browser/policies/managed/disable_sync.json