We are migrating from SP 2013 On-Prem to the cloud. We currently use Ping Federate as the idP for our external users, but we intend to use the native external sharing options online. Is there any way of doing user mappings or am I going to have to do this the long, hard way? I'm using ShareGate and I can maintain the metadata for those users, but it's the permissions for these external users that I'm sweating over. Appreciate the help!
Have you tried the CSV import for users? This should get your external users into your O365 tenant, then you can use the regular ShareGate user mapping functionality to correctly map the user permissions.
To migrate the external users, you'll need to find ways to do the following, probably with PowerShell.
- Get a list of external user email addresses from the SharePoint 2013 environment membership provider
- Cross reference that list with all the permissions assigned in SharePoint 2013
- Create an Office 365 external user invitation for each email address in 1
- Assign External user sharing permissions based on 2 and the invitation created in 3.