Why No, We Haven’t Droned On About The Original DOOM Enough
It was recently discovered that the original DOOM supported multiple monitors, and the way it does it explains why it took so long to figure it out. The support only exists in DOOM 1.1 and not later updates, further obfuscating the ability until it was revealed by Tech Tangents and shared on Hackaday. The source code is available, so if you want to try this you will need three copies and three computers to run it on … not to mention the monitors.
In order to play multimonitor DOOM, you need to connect three instances of the game on networked computers using the old IPX driver code DOOM used for multiplayer. Instead of bots or other people you spawn two drones which are locked to your first instance, that provide a viewpoint 90 degrees off of that instance. You set one drone to -left and one to -right and suddenly you actually enjoy DOOM with a view.
It is a bit of work, which may well explain why this support was dropped in later versions of DOOM, but if you want to experience one of the very first games that had multimonitor you have to expect to put a bit of work into it.