Bulk Invite Guest (External) Users to Site w/o Sending Invitation Email

Is there a way to bulk invite Guest (External) users to a site without sending off the invitation email?

The purpose would be to migrate all on-prem external accounts and keep all meta data intact as we are moving sites from on-prem to SPO. Then, once the site has been migrated (content, workflows, forms, etc) we would notify the specific users that the site is open and ready for use (cutover from op-prem to SPO).

The external users are from various domains and are going through the 4,000+ users to determine if they all need to come or only the "active" users. However, the thought is that some metadata may be missing the the user no longer exists in SPO.

Is there a better way to approach this?