Glenn McIntosh writes:
For some reason the distro wouldn't install with the new SSD on the fourth SATA port (failed during partitioning), but after removing the other disks and putting the new SSD on the second SATA port, it installed fine.
Double-check that the BIOS is using AHCI or NVMe, not "legacy" or "hybrid" mode.
What doesn't work: (1) with both SSD drives in place (Windows on the first SATA port), an attempt to BIOS boot to Windows appears to start the Windows boot ("Windows is loading files"), but then the system boots from the other (Linux drive); (2) also, update-grub on the Linux side does not find the Windows system. We ran out of time to try adding the chainload entry in grub.cfg by hand.
grub doesn't actually do the finding; that is carried out by a package called os-prober, which hooks itself into grub2's install/update scripts. Double-check that os-prober is installed.