I was lucky enough to be able to play Doom 0.9 when it had just come out as shareware (before the retail release) over IPX (on 10BASE2 cabling) across three machines so as to enable the 3-monitor-single-view mode.

IIRC, you set the middle one up as the server and launched the left and right machines/monitors with the -left or -right parameter accordingly.

It is with some wry amusement that I recently noticed that a few YouTubers over the past few months have only just 'discovered' this 'hidden' feature in Doom. ;)

Darnit, I'm old...