If you want to run an older OS have you considered just running a hypervisor like ESXi or KVM and then handling OS through that? There are lots of good solutions there at this point, and it can be a fun way to play with a lot of other cool features and different OS as well. You can even get near-native performance even for heavy duty graphics applications by using PCI passthrough. The only caveat that adds for hardware choice is that you'll want a processor with an IOMMU for the hardware virtualization support (AMD calls this "AMD-Vi", Intel "VT-d"). AMD is pretty good about not artificially segmenting there, I think everything modern they make supports it (all Ryzen/EPYC at least) though probably worth double checking overall system compat. Intel splits this all up more, Xeon always has everything but support varies elsewhere and you really just have to check the specs.
Even so that gives a ton of hardware choice and flexibility, and will give you more options to protect and control the systems beyond the OS themselves which is very important if you want to run something older since security patches will stop. But if you're judicious about what you use for what tasks and how you handle I/O it offers another option, and can make hardware changes a lot easier as well by abstracting away the metal somewhat. Basically a lot of the advantages that make virtualization so popular in general for business can be just as applicable at home these days, most of us have cycles and memory to spare and can afford to burn a bit of it on making a more pleasant software experience or working around issues coming from a higher level. In this case for example you could be running your Windows VM on virtual disks on a NAS/DAS or even the same system but supporting better snapshotting, and if the data was deleted simply roll back the entire VM to pre-upgrade state.
Even so that gives a ton of hardware choice and flexibility, and will give you more options to protect and control the systems beyond the OS themselves which is very important if you want to run something older since security patches will stop. But if you're judicious about what you use for what tasks and how you handle I/O it offers another option, and can make hardware changes a lot easier as well by abstracting away the metal somewhat. Basically a lot of the advantages that make virtualization so popular in general for business can be just as applicable at home these days, most of us have cycles and memory to spare and can afford to burn a bit of it on making a more pleasant software experience or working around issues coming from a higher level. In this case for example you could be running your Windows VM on virtual disks on a NAS/DAS or even the same system but supporting better snapshotting, and if the data was deleted simply roll back the entire VM to pre-upgrade state.