@Mr.Jeeves
FYI you will not see a drive in the boot manager unless the bios detects a valid EFI boot partition. This laptop does not support legacy boot.
The fact that you are seeing the drive show up in the storage manager means it is physically recognized and your drive and laptop are all ok. But there is no valid EFI boot partition (which would show up as a hidden fat32 partition on your existing SSD if it was present)
We would suggest following our windows setup guide and installing windows with a fresh install using a usb drive.
https://guides.frame.work/Guide/Windows+10+Installation+on+the+Framework+Laptop+DIY+Edition/92?lang=en