Well, yesterday... finished building the new PC, and after the usual gut wrenching moment when nothing appeared to be happening, it started just fine. Windows 11 announced this PC was not suitable (it fecking well is, mate, with that spec!) but I then realised what it actually meant was "you haven't plugged in your ethernet cable, so I can't verify that activation code".
Now, the long drag of rebuilding all the software, and finding Acronis True image 2017 is no longer available to me... bugger.
Capture One Pro now loads in about a quarter of the time, and so it should, with those nvme gen 4 drives. And 64GB of RAM helps.