There was a post[0] from a couple months ago for a piece of software called 'display-switch'[1]. It turns a simple/cheap USB switch into a n-computer KVM (however many systems the USB switch supports) by detecting the presence of the USB switch device on either system and switching the video input of the monitors using DDC/CI.

I've been using it for a couple of months and it's been a game changer. No more fiddling with monitor menus to switch inputs or wondering if the monitor is currently set to one computer or the other. You have to make sure your monitors support DDC/CI, though.

[0] https://news.ycombinator.com/item?id=29608967 [1] https://github.com/haimgel/display-switch