I recently bought the 32" 6k monitor from Dell. It has its own thunderbolt 4 hub and kvm and it works flawlessly! It gets upstream from my Mac from a single thunderbolt 4 cable and from my PC from an HDMI 2.1 and usb3 10gbps. On the monitor I have connected the Ethernet cable and my keyboard/mouse that switch to the correct machine with a keyboard shortcut or from the monitor osd.

I can even see both machines on my monitor simultaneously using the PiP capability.