A goal of mine a few months ago was to use both a joystick or gamepad on my 486 DX2/66 while still outputting MIDI music to my Roland units (MT-32 and SC-88ST). Games immediately relevant for this: Wing Commander 1&2, Zeliard.
I recently got a lot of: Gravis Gamepad, Gravis Gamepad Pro, Advanced Gravis Stick and its later 2 button+trigger on the stick successor.

I only owned the DB15midi adapter from Serdashop, but this monopolizes the whole gameport and doesn't allow a joystick. So I went on aliexpress (big mistake in retrospect):

These cables from aliexpress are really crappy:
https://www.aliexpress.com/item/32917493914.h … searchweb201603_

After a bit more than a month of shipping, here were the pinouts I got compared to what could have been:

Male connector to PC:
1: 5V
2: button 1 (no wire)
3: x axis (no wire)
4: GND
5: redundant GND (no wire)
6: button 2 (no wire)
7: y axis (no wire)
8: redundant 5V (no wire)

9: redundant 5V (no wire)
10: button 3 (no wire)
11: x2 axis (no wire)
12: MIDI out or b3/b4 GND
13: y2 axis (no wire)
14: button 4 (no wire)
15: MIDI in

Split Joystick female connector:
Basically only 5V and GND got to it, which is totally useless.

Split MIDI OUT:
This was wired correctly, making it the only thing that works on the bloody thing.

Split MIDI IN:
Although I have a rock band 3 keytar from the xbox360 days which could be used, since it has absolutely no resistors, no optocouplers, it's a big NOPE in terms of testing it out. My needs are taken care of elsewhere for midi input (modern windows machine and eventually a SE/30 with cubase 1)

So, I had to do the rewiring and the DB15MIDI is awesome to have in this solution for MIDI out, the PCB has some buffering and resistors all included, making it just a simple wire solder job. Here's the final look:

To do:
1) decide whether I want to bother with B3 and B4
2) decide whether a 2nd joystick/gamepad is needed *with* hardware MIDI output in games (probably not! unless you guys know of an example)
3) get rid of an unwanted signal on B3 whenever B1 is pressed (I guess the individual wire tubes were not enough in this specific case and a connection was made by squishing the wires in the casing)
4) shrinking those tubes
5) Get a 3rd DB15 casing, a quick search late last night on digikey revealed absurd prices on these connectors (the cheapest was a few dollars...what?)