Using an old VGA KVM for keyboards and mice?

I grabbed an HP E27u QHD monitor to replace a FHD Samsung with a heavy surplus discount, so I have no hope of finding a KVM with HDMI that can properly drive a QHD panel without spending a ton of money. My end game is just to get rid of a 2nd keyboard and only run one. I looked into an old KVM from the VGA era, given how many are out there and how cheap they are. The main thing is that the ones I am looking at have USB and not PS/2, so that is not an issue. I can run the systems through the monitor with the PC being on DP, HDMI for the the M1 Mac Mini and USB-C for the 16" 2021 MBP.

Has anyone ever done this without issue, short of needing to move the display cables or use multiple connectors? The PC is on DP, the Mac Mini is on HDMI, and the MBP is on USB-C. If need be, I can make a dummy adapter by buying some VGA headers online and soldering 75-ohm resistors on all three ends.