My old setup at this workstation was this RISCOS machine and a Win7 one sharing monitor keyboard and mouse. Video is DVI-d and keyboard etc PS2. The feed from the KVM to monitor (DVI-d) was split to DVI-d and HDMI, to allow the TV above the workbench to display circuit etc diagrams. All worked just as I wanted.
Decided it was time to 'upgrade' to Win10. Which I'm actually quite happy with.
Old PC motherboard wouldn't take Win10, so bought a new expensive ATX bundle. Hoping it would give me another 10 years or so.
Its onboard video out is HDMI. The DVI-d graphics card from the old MB won't work with the new MB. A passive HDMI to DVI-d lead didn't work - even direct to the monitor.
Ordered up an active HDMI to DVI-d converter. That does work direct to the monitor and through the KVM switch - but not with the DVI to DVI/HDMI splitter (for the TV) in place.
Seems to be one step forward, one back.