I have been given a task to merge 3 AD forest and make it one. following is the current scenario
AD 1(forest A) - local AD for system login ,2300 Users
AD2 (forest B)- synced with Azure AD and has online mailboxes Windows Server 2016 -forest level 2016(previously on-premises exchange server now decommissioned) 350 users
AD3 (Forest C)- synced with Azure AD and has online mailboxes server 2012 R2- forest level 2012 R2 (previously on-premises exchange server now decommissioned) 2000 users
looking for expert opinion to merge all 3 AD s and make one without creating problem to system Login on desktops as well as cloud features like mail ,SharePoint etc.