The chances are HP TRIM will have been implemented many years ago and typically, we find that the meta data requirements have changed over the years meaning the migration of metadata often requires transformation.
In terms of ETL, the extraction process is straightforward however, the transformation part often merits bespoke scripts to update the metadata to the standards now required in the new destination, SharePoint online. Failing this, we work with the client to manually update the metadata prior to the loading process. Loading the data into SharePoint can normally be performed using a third-party product such as Sharegate.
Migration of HP Trim documents to SharePoint O365