Due to historical issues, our company currently has on-prem AD (authenticating for user accounts, network access and all internal applications) and Azure AD (using for Office 365 products). Since both are having separate accounts (for example: firstname.lastname@example.org is the on-prem AD account and apparently email@example.com is Azure AD user account in O365).
We're researching a solution that can support integrating or synchronizing the accounts of the on-prem AD and the Azure AD.
P/S: we research the Azure AD connect, but that's applicable when there is a fresh on-prem or Azure AD. But for our case, there are existing accounts at both.