Project Solution can assist with your initiative for migrating and upgrading your SharePoint Server/Online Deployment; including migration and upgrade of  on-prem deployment of SharePoint Server, migrating from on-prem to the cloud i.e. Microsoft SharePoint Online and from one Online environment to another for example when development or training instances are needed to be maintained as mandated by internal policy/requirement. 

We use our own, fully supported, packaged migration tool to migrate content.