Upgrade Existing SCCM Infrastructure and Windows Server OS version

Hi All,

I have to upgrade our existing SCCM infrastructure to the latest version along with Windows OS and SQL version. Additionally, I want to remove our existing CAS to simplify the environment. I was wondering what is the best approach to do that. Below is the existing setup and appreciate it if anyone can lead me to the best approach based on the existing setup.

• Existing setup
  • Three Windows Server 2012 R2 Servers as below.
    • CAS Server
    • Child Primary Site
    • Remote SQL 2012 SP4 Standard

• Options as for my understanding
  • Option1: In-Place upgrade
    • In-console upgrade to the current branch version 2103 and remove the CAS.
    • In-Place upgrade from Windows Server OS 2012 R2 to Windows Server 2019
    • In-Place upgrades of the SQL version.
    • In-Place upgrades of the SCCM version.
  • Option2: Backup and Restore
    • In-console upgrade to the current branch version 2103 and remove the CAS.
    • Backup and restore the infrastructure with the newer Windows Operating System (Both Remote SQL and Primary Site).
    • Upgrade to the latest supported SQL version (SQL 2019 Standard)
    • Upgrade to the latest SCCM versions.
  • Option3: Side-by-Site Migration
    • In-console upgrade to the current branch version 2103 and remove the CAS.
    • Implement new SCCM infrastructure with a new Remote SQL server
    • Migrate contents to the new infrastructure
  • Option4: Implement a fresh environment

Thanks in Advance
Dilan