You can do this with even less fiddling just by getting a KVM that supports video. There are reasonably priced ones that can even do 4K 60Hz. This also means you don't have to deal with monitors that don't implement input switching via DDC/CI (thanks LG).

I did that at home. But I needed to try several KVMs until I found one which was stable. And I hate all the cables.

I agree that the industry hates its consumers and likes to mess things up. CEC never always quite the same. Not supported on many GPUs etc.

I do not want to appear to condone LG. But actually (sorry!) some supoort[0] it using DDC side channels (0x50 rather that 0x51). But I agree it is painful. Yet I prefer it over my cable spaghetti.

[0] https://github.com/rockowitz/ddcutil/wiki/Switching-input-so...

Last time I looked (which was some years ago), I couldn't find any that support display over Thunderbolt without resorting to DisplayLink.

it's much more reasonable and trivial on lower quality monitors but if one of the two PCs is for gaming you're going to want 4k at at least 120Hz which, last I checked, didn't exist (or was very expensive). You also might have a hard time finding one that takes DisplayPort in, which is preferable for Linux.

Personally I just run the USB devices into a $5 USB A/B switch and manually change the inputs on the monitor.