ADFS with Azure MFA disconnected forests

Question

I have 2 domains that are setup as follows

domain1.com currently setup with o365 and have Azure MFA enabled this domain is currently synced with Azure AD with AD Connect and has an ADFS Farm that uses MFA.

domain2.com is disconnected from the other domain for security purposes and has an ADFS farm which we need to have MFA enabled on. We would like to utilise the MFA thats been setup under domain1 but at the moment this is not possible due to the upn for domain2 not being available on Azure AD.

domain1 is a corporate domain
domain2 is a technical domain which we need to maintain the security boundary.

Answer 1

We have workshops to help move off ADFS https://techcommunity.microsoft.com/t5/community-events-list/microsoft-workshops-how-to-successfully-migrate-away-from-ad-fs/m-p/3668480 & https://www.microsoft.com/en-us/security/business/identity-access/upgrade-adfs