Thanks Matt, I'll keep that in mind! For now the plan is still to simply buy a NVMe adapter and a Samsung 970 M.2 drive though, and then use Samsung's own free Data Migration software (which only works with Samsung drives, but that's fine in this case) to clone the disks, after which I will swap them.

The "old" 512 GB disk I'll then use in a new desktop system I plan on buying in a couple of months. I'll use it as a boot disk. For my desktop PC, this is enough to contain the OS and all of my programs. All my other stuff like music, photo's etc is on a secondary drive anyway.

To be honest, I find it a bit surprising that only so few NVMe to USB solutions exist. NVMe has been there now for some years already, no? For SATA to USB, literally hundreds of adapters exist. Strange.