Currently, performing a content search of OneDrives across a multi-geo environment isn't possible, it only searches the default Geo, not satellite Geos. If you create a security compliance filter targeted at your satellite geo and put the eDiscovery person in the role, then they can search that satellite geo. Please update oneDrive content search to search across geos the same way that an Exchange mailbox search works, without requiring adding/removing them from security compliance filters. (This workaround was the result of working with Microsoft Premier support, so it's legit.)