Great write-up! But how about this situation?
Existing DB server is remote - let's call it SCCMDBOLD. The plan is to migrate this SQL server to new hardware (SCCMDBNEW) and KEEP the same name. The plan is to build a new SQL server, copies databases etc etc, rename and re-IP the new DB server to be like the old one.
What steps do I follow then? Same as the steps you outline except when the time comes to run ConfigMgr setup will it let you fill in the EXISTING same database server name?
Every procedure I have found talks about moving to a new DB server with a NEW name. What if you are keeping the same name?
Also - why wouldn't you run preinst.exe /stopsite before running the DB backup and restore? Couldn't the DB get out of sync?
Yet another question - in your screenshot of the preinst.exe /stopsite - how does SCCM already know about DSGSQL1 if you haven't run the setup wizard yet to tell it about the new server?