Hello there,
The best way is to disjoin and rejoin the Session host server and once you have joined wait for replication and reboot the server.Before that take a snap of the server .
Migration for a Remote Desktop Services deployment is supported from source servers running Windows Server 2016 to destination servers running Windows Server 2016. In other words, there is no direct in-place migration from RDS in Windows Server 2012 R2 to Windows Server 2016. Instead, for most of the RDS components, you first upgrade to Windows Server 2016 and then migrate data and licenses.
Migrate your Remote Desktop Services deployment https://video2.skills-academy.com/en-us/windows-server/remote/remote-desktop-services/migrate-rds-role-services
Hope this resolves your Query !!
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