The connector shown in the article is apparently the 24-pin connector known as the Open Maintenance Connector (OMC). It's located in the electronics and equipment bay under the nose of the Boeing 737 NG and 737 Max.

I say "apparently" as I had Gemini identify the port from the image.

The OMC provides direct access to key avionics data networks, including the ARINC 429 buses that link the pilot's Flight Management Computer (FMC) to the Multi-Function Control and Display Unit (MCDU).