[FrankenPC]

Side note: I have the direct opposite wish: I want a single mouse that can move off the boundary of one PC's monitor(s) and into the monitor of my laptop or across two or more desktop computers without having to change hardware. Same thing with a single keyboard.

[anotheryou]

https://symless.com/synergy (there is also an old freeware version floating around if you google a bit)

Used to be the first thing I installed when setting up another computer.

[btschaegg]

I can second this recommendation. I don't use it much nowadays, but it's done good work for me in the past, and I've gladly paid them the 20$ for a Pro license.

I have to say that they haven't grasped the whole "open source on GitHub" thing yet though. It took me over a year to get a PR accepted that fixed a simple Qt5 #include problem...

[SteveNuts]

Does it have working encryption yet? It's been a while since I've used it, I stopped because at the time you were basically sending all keystrokes in plaintext over the network.

[maxxxxx]

On Windows there are quite a few software packages that do this. On some you can even drag files from one device to another.