Note that it is definitely possible to use this without those horrible dongles and even if you don't have any spare video ports at all.

Unfortunately, on both Windows and Mac, open-source solutions don't exist because no single developer wants to deal with driver signing.

On Linux, you can do this a number of ways:

- the evdi kernel module can create fake video outputs (I'm currently working on a CLI for it - stay tuned)

- xrandr can force-enable disconnected video outputs (I believe even if you've used up all the CRTCs)

- xrandr with Intel drivers can create virtual screens

- swaywm has a config option to make virtual screens