Workload question on co-managed PCs where SCCM server got decommed

[GregEFX]

Hi, I'm new to Intune so apologies for asking something probably already covered. 

I learned recently that we have about 100 or so systems that are co-managed with SCCM, but our SCCM server got decommissioned before I was brought onboard, and these co-managed PCs show status as follows: 

Configuration Manager agent state

Could not connect

I have attempted the following on a test machine: 

remove the SCCM client and registry entries

retire the PC and remove Intune entries

remove the device from AAD

re-enroll the device into Intune

These are all hybrid-joined from on-prem AD and I have a feeling the fix is to replace the machines.

What is the best process to get these machines using Intune only for managed apps and compliance?

[#2]

Hello GregEFX ,
What is the status shown for these machines after applying these actions ?
remove the SCCM client and registry entries
retire the PC and remove Intune entries
remove the device from AAD
re-enroll the device into Intune

[#3]

Try to delete MDM :policies then contact your vendor to generate a new request (a signed CSR)