I'm planning to upgrade to Apple Silicon as well and did some research on it.
You can use
https://isapplesiliconready.com to see that almost no cloud service is offering native support at the moment. Not Dropbox, not Microsoft, not Sync, nor any other provider.
Microsoft recently committed to offer full native support in the future:
We’re excited to share some of the updates and improvements we’re in the process of making to OneDrive running on Apple products Redirect your important Mac..
techcommunity.microsoft.com
The important thing is, that it is using the new "File Provider" framework from Apple. No other service is doing that at the moment. Only Expandrive Strongsync offers a (expensive) third party sync client.
Google just now transitioned to the new "Drive for Desktop" client:
https://support.google.com/googleone/answer/10309431?hl=en — but it requires users to allow kernel extensions in recovery mode and stuff like that (
https://support.google.com/a/users/answer/10444081). It is not based on the new File Provider Framework and I doubt they will rewrite their newly launched app.
So for now (besides iCloud that is missing too many features for me) Microsoft OneDrive seems to be the best bet for the future.