No, if you mean old migration from Ubuntu to SuSE - that does not work.

However if you install your new SMG virtual appliance then you will have a new option:

On the other side your (smart) approach will work too I assume ...

Is there any docs on that?

, that is almost a running joke ... SMG and documentation. I think official documentation is pretty old (too old; 2021).

I migrated a server this summer - before this feature ha been offered. However I played around a little bit with the new feature in fall - it does not harm your old server. So you can continue with your old environment if migration failed (Especially if you take a snapshot ).

I copied the vastorage volume to the new GMS server and it work.   So that looks to be the way to upgrade.