That
console is probably based on an off the shelf, industrial computer board with ISA peripherals. The daughter boards are probably for parallel printer ports, the
DMX interface, input/output for faders, buttons, and indicators. It might have an external video card, especially since it has the proprietary, remote video on
XLR.
Chances are the
ethernet jack was just there because off the shelf motherboards came with one.
Network printers were rare at the time, and it would not have any printer drivers for a modern one. I doubt that
ethernet was used at all for a lighting
system in those years.
I suggest not attempting any updates, even if you manage to find one. Performing updates in that era was not painless and reliable as it is now. Without any factory support, you could turn it into a door stop.
I would worry most about a hard drive failure. If you can find new
stock of a compatible drive, and a vintage computer and software to do it with, clone the existing drive soon. A hard drive failure is inevitable.