Hello Joey Blaydes,
Thank you for posting in Microsoft Community forum.
Will Server 2022 ADCS (Certificate Services) work with/or an 2008 r2 AD Functional level?
A: I think the 2022 server can be joined to 2008 R2 AD domain
Functional levels determine the available Active Directory Domain Services (AD DS) domain or forest capabilities. They also determine which Windows Server operating systems you can run on domain controllers in the domain or forest. However, functional levels do not affect which operating systems you can run on workstations and member servers that are joined to the domain or forest.
Reference:
Forest and Domain Functional Levels
Active Directory Domain Services Functional Levels in Windows Server | Microsoft Learn
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Daisy Zhou