While browsing some old hardware magazines and forums, I collected some informative facts about proprietary local bus hardware:
First available mainboard providing a local bus was the "486 Superboard" by Orchid in early 1992.
It featured an Opti Chipset and an EISA-style local bus connector called "convertible slot".
This "Orchid local bus" or "Opti local bus" design was adopted by many other manufacturers.
First available graphics cards by Orchid were called "Fahrenheit 1280°D" (S3 911) and "Prodesigner IIsD" (ET4000AX). Several clone cards with these chips were made. Later, an IDE caching controller was also available, the "Tekram DC-660"
ET4000AX_LB.jpg
Gigabyte featured the "GA-486US" mainboard using two consecutive 16 bit ISA slots for local bus interconnection.
Available cards were "GA-200" (ET4000AX), "GA-300" (S3 911) and "GA-400" (SCSI)
GA-486US.jpg
ECS Elitegroup offered local buses on their "UL486" and "FX-3000" a.k.a "US3486" motherboards using the 112-pin MCA slot we all know from the later VLB.
But ECS's implementation is not VESA compatible and unfortunately visually not distinguishable!
Suitable cards for the "ECS local bus": "VI-811" (ET4000AX) and "VI-911" (S3 911)
UL486.jpg
Chips & Technologies offered a "Wingine local bus" on their 82C4021 chipset based motherboards for their
Wingine F64200 DGX Accelerator cards. These motherboards also had one VLB compatible slot.
wingine.jpg
Another different local bus connection was used by Joindata with motherboard models "G486PEL" and "G486PLB"
Peripheral cards are "G-HOSTS3" (s3 911) and "G-HOST4000" (ET4000)
GHOST4000_LB.jpg
There are more proprietary sytems like the Hauppauge 486M, NEC "Optibus", but it is nearly nothing is known about them.