Query on Moving\Migrating SCOM 2021 R2 to Azure

Hi,

If you want to do an in place upgrade of SCOM, it will need to go from SCOM 2012R2 -> SCOM 2016 -> SCOM 2019 (UR1).
https://kevinholman.com/2019/03/07/scom-2019-news/

I would prefer to do the upgrade on-premise, and afterwards move to Azure.

The difficulty will be the supported SQL/OS version for each SCOM version. 
SCOM 2016 OS: (Windows Server 2012 & 2016)
https://docs.microsoft.com/en-us/system-center/scom/system-requirements?view=sc-om-2016
SCOM 2019 OS:  (Windows Server 2016 & 2019)
https://docs.microsoft.com/en-us/system-center/scom/system-requirements?view=sc-om-2019

SCOM 2016 SQL: (SQL 2012, 2014 & 2016)
https://docs.microsoft.com/en-us/system-center/scom/plan-sqlserver-design?view=sc-om-2016#sql-server-requirements
SCOM 2019 SQL: (SQL 2016 & 2017)
https://docs.microsoft.com/en-us/system-center/scom/plan-sqlserver-design?view=sc-om-2019#sql-server-requirements

So depending on your current situation, you can:
OS: Do an in place upgrade or install new management servers and remove the unsupported OS ones

SQL: Do an in place upgrade or move the databases to a new supported SQL environment. 
https://docs.microsoft.com/en-us/system-center/scom/manage-move-opsdb?view=sc-om-2019
https://docs.microsoft.com/en-us/system-center/scom/manage-move-omdwdb?view=sc-om-2019

The biggest bottleneck will be the VMs hosting the SCOM SQL databases (disk latency). Carefully choose your machines that you will use. Use these articles to check on the available performance:

 https://docs.microsoft.com/en-us/azure/virtual-machines/windows/sql/virtual-machines-windows-sql-performance

 https://docs.microsoft.com/en-us/azure/virtual-machines/windows/premium-storage#scalability-and-performance-targets
For the Management Server a DS2 machine will do.

Have fun Migrating!