Teams Users Migration from onmicrosoft.com to domain.com ( Same tennant )

Hi anthonygderealone ,

for this purposes, you need to setup Azure AD connect and an Exchange Hybrid scenario.

Your OnPrem accounts will be linked to your O365 accounts with Azure AD Connect. Afterwards your users can access Teams with their AD OnPrem account.

But I would suggest asking a local Microsoft partner in supporting you in this project.

Here are some links with further informations:

https://docs.microsoft.com/azure/active-directory/hybrid/how-to-connect-install-existing-tenant?WT.mc_id=M365-MVP-5004286

https://docs.microsoft.com/azure/active-directory/hybrid/how-to-connect-install-select-installation?WT.mc_id=M365-MVP-5004286

https://docs.microsoft.com/exchange/hybrid-deployment/hybrid-deployment?WT.mc_id=M365-MVP-5004286