Hello @EnterpriseArchitect
Here is a step-by-step guide for setting up ADFS 2.0 for Office 365 for Single Sign-On. However, the process is same for ADFS 4.0 as well.
As you have already setup ADFS environment and users are synced to Azure AD, all you need to do is run below commands from the Primary ADFS Server to configure federation between O365 and ADFS.
Install-Module MSOnline
Connect-MsolService
Convert-MsolDomainToFederated –domain < your_domain.com >
Then configure the ADFS Service Name to local intranet zone on all the client computers in your environment. You can use GPO for this purpose as well. This is required to facilitate WIA (Windows Integrated Authentication) so that existing NTLM or Kerberos tickets can be used for authentication and you will not be prompted for authentication.
You can refer to this documentation for configuring ADFS to use Azure MFA for 2nd factor authentication.
For best Seamless SSO experience, I would suggest you to go with hybrid Azure Active Directory join for federated domains
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