Teams B2B sync on macOS

Hi all,

I have set up B2B collaboration between two Microsoft 365 tenants. Each tenant has its own Teams environment and users can switch tenants inside the Teams app without any problems. Both sides would like to work in each other's Teams channels and they also want something very specific. They want OneDrive on macOS to sync both their own tenant’s files and the other tenant’s files locally in Finder.

This is where things break.

• Everything looks correctly configured.
• B2B collaboration is enabled on both tenants
• Guest access is allowed
• Sharing settings are set to the least restrictive level

When a user opens a SharePoint library in the other tenant and clicks Sync, the OneDrive popup shows up and macOS asks to open the OneDrive app, but then nothing happens. No new library appears in OneDrive and there is no error.

My question is whether this is simply an expected limitation. Can OneDrive on macOS actually sync document libraries from a different tenant when the user is only a B2B guest? Or is this not supported?

I have seen mixed information. Some people say guests cannot sync cross tenant libraries at all. Others say it only works when the team is set up as a Shared Channel. Before restructuring everything I want to confirm the real behaviour.

Do I need to create a Shared Team or Shared Channel to make cross tenant file sync work in Finder? Or is the missing sync just how OneDrive behaves for B2B guests on macOS?

Any real world experience would be very helpful.