Cathode Ray Dude made a video, and a picture on Wikimedia is from his video.... https://www.youtube.com/watch?v=s4HAqGrJFCU at 16:50 it makes an appearance.
Maybe the user NetFreak on this wiki can get a photo inside the back panel?
https://wiki.preterhuman.net/Gateway_2000_Destination_D6-266
It does seem there was a revision of the system.
This page has a shot of the back, and a game port is on the mainboard. The voodoo betrays where PCI cards end, next modem, then nothing. So in this Destination the audio must be onboard.... and are some ports blanked-off below the gameport? The A/V panel on the back, or its wring, might be different to yours.
https://wisconsincomputerclub.com/index.php?t … 36-monitor.227/
The ebay auction you found clearly has no gameport on the blanking plate, so that Destination must have had a card originally. That harness I think is the one for your card. Maybe the seller will open it up and take some photos, although if it has been on the 'bay for a month already, the seller might just take a very low price to get rid of it.
Good luck