How to integrate custom hardware?

Third party integrations
1

I’ve created a very basic board that has an Ethernet jack and several relays. This allows me to control 120V devices through a basic webpage.

Can anyone point me to where I can start to read on how to integrate my board into HA?

2

I always prefer to do everything over MQTT

3

Depending on the web page interface, you might look into a rest based switch.