Do you want to turn on sync in Microsoft Edge Chromium?
After researching, I think there's no such group policy to turn on sync in Edge. We can only turn it on manually for now. I also found a thread about this. The official account also said there's no such policy now.
If you need this feature, you can send your feature request through Send feedback button (Alt+Shift+I) in Edge.
Thanks for your understanding.
Best Regards,
Yu Zhou