Hey guys, this post helped me a lot so I'm paying back by sharing my setup that works for me (mostly
Macs that I'm connecting to Pro Display are MacMini M1 2020 and MacBook Pro 14" M1. So both are recent and has DSC support (so they can do 6K resolution through DisplayPort 1.2 link).
Parts
This is what I am using (all parts was easy to buy on Amazon in EU at the time of writing):
- Apple Pro Display XDR (obviously)
- Thunderbolt cable that was included with display. Connect it to Wacom Link port marked for display, the other end goes to XDR thunderbolt port. If you don't have that cable anymore, usbc cable that comes with Wacom Link also works.
- Wacom Link Plus. You need to power it with separate usb-c power adapter. You have to buy it (cable as well or use included) if you don't have it. It does not need much power, so the one from iphone will do. There are reports that connecting it to computer port does not work.
- miniDP to Display port cable. I bought not-so-expensive-one on Amazon "Silkland Mini DisplayPort to DisplayPort 1.4 1M, 8K@60Hz". Connect one end to Wacom Link and other end to KVM
- micro USB to USB cable. This one included with Link. Do Wacom -> KVM as well.
- KVM. I had good experience before with one from ATEN (which is professional-grade equipment). On the other hand StarTech dock that I have was piece of cagal from the start. So I bought Aten CS1922 DisplayPort 1.2 KVM. There is more expensive version CS1922M. It have more gizmos like combining sources to one display, but I didn't need it. They have even more options, go to aten.com and pick the one you need. There is new sexy one coming soon. They all 4K (DisplayPort 1.2). Description say they can not do 6K, but that's fine if your graphics card able to use DSC
- Two usb-c to DisplayPort cables *bidirectional* (this is important). I got recommended ones from Club3D CAC-1557. Also they are Dutch and I am in The Netherlands

Connect them between KVM and those macs of yours.
- Also connect sound and usb-cables between KVM and macs. Aten have these cables included in KVM package.
- Keyboard and mouse setup I'll leave to you as there are many options. I use wireless non-mac ones that can switch between sources themselves.
- Some velcro tape to reduce the mess
Does it work?
Well, most of the times. KVM works quite fast. Switching takes 2-4 seconds. I have full 6K resolution for both inputs.
But sometimes picture does not show and the only thing that helps is to disconnect and connect usbc cable from the mac. Which is annoying.
It happens mostly when non-active input is not used for a long time. When I'm switching back and forth between macs during the day - it's fine.
Also what I've noticed - when inactive, mac goes into headless mode (like there is no display connected at all). This is on contrary with other setup with usbc-DVI dual-link that I had before with gorgeous Cinema Display 30. There inactive mac still thought it connected to display. So maybe that black screen is mac os misbehaving and not hardware-related, dunno...
Okay, that's it folks. I hope it will help someone.