I *only* use server/workstation hardware, server chips (xeon/epyc); ecc, etc and have been using virtualization both production/work and at home for well over 30 years (well over 40 years if you include mainframe virtualization). 'type 2' (as vmware/others like to market it) hypervisors do not do passthrough as you indicate (well except for hardware assisted passthrough (Vt-x/amd-v/iommu)). That being said they do a good job of shared graphics call mapping.
QEMU supports it, last I checked, and it's a type 2 hypervisor. KVM also supports it, but it's type 1. I
think VMWare supports it, but I don't work with it so I couldn't say for certain.
Shared graphics call mapping is the messy pile of crap I was talking about because it requires special guest drivers, special host drivers, and for your guest application to limit itself to a relatively specific set of supported APIs. It's also historically been messy when using APIs in a guest that aren't supported on the host.
In any case, most VMs of either type will offer
some form of USB port passthrough to get your mouse working at least.
full device passthrough (vt-d/sr-iov/etc) works rather well actually and has for a long time (well for the last 15+ years on PC, much longer on other platforms (IBM has been doing that since the 70's)).
SR-IOV on x86 wasn't really a thing until the mid teens, unless my memory is failing me, and has only become a common feature on consumer gear in the last couple years. VT-D has been common significantly longer - I remember it showing up in consumer x86 gear around 2010ish.
Regardless, since you clearly know what you're doing, you should be
well aware of the limits of host/guest GPU API call translation. It's not the developer's fault that a unity feature relies on a call that's not well supported by that mess of a system, and frankly expecting them to fix it is kind of silly. You can try forcing unity to use a different API - if there's an issue with a specific DirectX call not getting translated or handled correctly, OpenGL might work better.