Ugh. The rabbit hole goes deep. Now that I have three machines connected and the LG's remote being flaky, switching inputs of a monitor, a BT keyboard and a BT mouse is getting painful.
I thought I could make the input selection follow the keyboard, but DDC is not supported by my monitor. So I thought, an IR blaster might do the trick.
I have a ESP32 sitting around from when I thought I'd turn the Disk Drive slot on my Mac Plus into an LCD info panel, but i've now mounted a USB/SD Card Reader hub in that space.
So now looking at building at an IR Blaster accepting HTTP posts to switch the monitor and each computer sends the command when the keyboard connects to it.