Checking status of Motorola RLN6506

I have a Motorola Minitor VI, which has a base station with a 6-pin DIN plug with the following functionality:

Relay Dry Contact Closure (Pins 2 and 3)
When the accessory relay is energized, its contacts close and present a short across pins 2 and 3 of the connector. The relay contacts are rated for 10 watts maximum at 28 VDC/ACRMS. Within the limits of the 10-watt rating the closed contacts can handle up to 750 mA continuously and switch up to 400 mA of current. Relay contact rating: 750 mA maximum @ 28 VDC.

I’m at a loss for how I can link this to HA so that I can trigger an automation when the accessory relay is energized (A page is received).
I suspect that I could go with ESPHome, an arduino, or a RPi, but I’m unsure what the easiest way to read this would be.
Where should I start?