Anything that can do better than 1080p is insanely expensive or cheap and flakey. I gave up looking and just got a new monitor with a KVM built in.

Most have one USB-C with 65w+ PD which includes the keyboard and mouse and then add 1-3 more slots that have HDMI and/or DisplatPort + USB-A for the keyboard and mouse.

Keen to know what you've tried. Or if anyone has found something good that isn't silly expensive or cheap and dodgy.

I wanted something similar from a remote company I was working for. They were pretty good about fulfilling requests, but when I asked for a good kvm switch they said they had trouble in the past and instead recommended a usb hub that can toggle between machines. Then connect both machines to the same monitor and toggle the input. Not ideal, but low cost and functional. Might not suit your needs (would be annoying if you have to frequently toggle back and forth), but if you're just trying to share your desk space between a work machine and personal, and the monitor input is easy to toggle, it's worth considering.

Tbh, just run the Ubuntu box headless and ssh into it. You can do anything you’d need to. Even better, swap it to Debian or something like that, because Ubuntu is unfortunately kinda undergoing gradual enshitification lately.

I tried a USB KVM switcher. I only recall there were serious issues and it didn’t last long.

Now I use a high quality USB dock and physically unplug/re-replug a work and personal laptop. That’s been a simple and reliable solution.

For my home server, I ssh into it.

I picked up one of these ugreen displayport KVMs a couple months ago and so far have been happy with it:

https://www.amazon.com/UGREEN-Displayport-Support-Monitor-Keyboard/dp/B0CFFFHFJT

The only issue I have had is that if I'm switched to computer B and computer A goes to sleep, I cannot wake it up through the switch. This was not a deal breaker for me because I have easy access to the power button of both computers. I wonder if this issue may be resolved by powering the switch with a USB-C power plug, since it otherwise requires USB power from both computer connections.

Make sure that, whatever switch you want to get, the switch supports simulating output (edit simulation/storing) and USB devices. Otherwise every switching action would cause disconnect and connect actions on the hosts.

One of them is a laptop, why ssh to the server isn't an option? Set up tmux on the server so it always connects to the same session, so you can just continue where you left last time. If you need desktop support, rdp in gnome works really well.

E.g if you connect with this command, and tmux is installed on the server, it will start a new session named "main". If a session with that name exists it will connect to that:

ssh -t pi@192.168.1.2 tmux new-session -A -s main

Add something to .bashrc on the server to always do the same if you work on that phisically:

if command -v tmux &> /dev/null && [ -n "$PS1" ] && [[ ! "$TERM" =~ screen ]] && [[ ! "$TERM" =~ tmux ]] && [ -z "$TMUX" ]; then
tmux new-session
fi

I have a similar setup and in the end just went for a cheap chinese („ESKEVE“) 4x HDMI 2.0 KVM switch that supports 4K60. No problems except HDR does not work properly, which is not useful on my monitor anyway. Laptops are on USB-C docks with HDMI 2.0 out, PC uses a passive DP to HDMI cable.

I've been very happy with my Monoprice "Blackbird 4K DisplayPort 1.4 USB 3.0 4x1 KVM Switch, 4K@60Hz, HDR, YCbCr 4:4:4, HDCP 2.2". I run an ultrawide at 3840x1600 @ 144 Hz, or HDR at 120 Hz, G-Sync both, and it works wonderfully. It took some effort to get all the required devices using the same connections - went through quite a few "USB-C to DP" cables from Amazon that had to be returned because they couldn't do the high refresh like they claimed ... but once I got everything set up, it's worked like a dream, 3+ years and counting now I think.