I subscribe to iCloud, OneDrive, Dropbox and Google Drive.
I’m about to transfer the data from my old Windows 10 laptop and several external hard drives to the cloud. I want to mirror all the data in each account.
Is the best way to do this to upload all the data to one account and then use something like https://www.multcloud.com to synchronize the data to the other accounts? Or am I better off syncing all of the data through my laptop to each account one at a time?
You reminded me of a tool I came across a long time ago and wanted to try, but never did get around to. https://stablebit.com/CloudDrive
This tool is not designed specifically for what you want, although might be able to achieve it with one of its features.