We are currently exploring the possibility of migrating data from OneDrive for Business to Nextcloud.
Before moving forward, I would like to ask if anyone in the community has experience with a similar migration.
In particular, I am interested in understanding:
Whether such a migration is feasible in practice
Any general challenges or limitations encountered during the process
Experiences from environments with a relatively large number of users
Hi, I have no experience with OneDrive or Microsoft, but there would be the idea
to migrate slowly, meaning first with a subset of unimportant folders to
be synced, computer by computer. … this is just an
idea though 
…
One issue with Nextcloud when starting a set up is to have all the data synced across the devices. E.g. in general, you’d probably need to populate the server with data (not sure if you can do that for all the users with OneDrive) and then the user’s have to set up the client software on their device and sync everything for a first time.
Not sure if it might work to tell the users to disable the OneDrive, then install the Nextcloud sync client and sync exactly this folder to Nextcloud. That would probably my preferred method for a single user that wants to migrate but not for a larger organization.
For you it is just the user data you want to migrate or as well shares between the users and/or public shares? Beyond data, if it is shares and stuff, I don’t know of any public tools, perhaps you can do something using the Nextcloud APIs and let a script do the job?
I’ve done this before and we need to keep all the files on the device.
We also have SharePoint sites but for now our priority is to move the user’s personal data to their Nextcloud account.
And I’d first to try to backup everything, so worst case you can restore manually everything for a user.
For the server part sync you could try using rclone - https://rclone.org/ - I never tried, but Onedrive is listed as a supported provider.
If you sync server side via rclone and then locally on desktop sync use the same local drive as sync destination I think it should work without the client having to sync everything back and forth.