If anyone is working with a JetKVM and needs a DisplayPort to HDMI adapter that works then this lower cost device seems to do the trick:
https://www.amazon.co.uk/dp/B081GMCNNF
~£7 or so and seems to work with the test machine I have here (an HP Prodesk G4) which only offers Displayport output on the unit I have (an HDMI module for the HP is available).
You might come across USB issues with the HP Prodesk devices and the JetKVM but you can alter the USB HID setting for the JetKVM via the Settings -> Hardware -USB Devices section
Not having a Grub boot menu to switch between Kubuntu and Windows 11 would probably help here
The KVM seems to be working in Windows 11 and Kubuntu.