If I were to tackle this project, I’d use an ESP32 and a relay with 120V contacts. That way you can use a GFCI receptacle and be code compliant if your darkroom is in a basement or the enlarger receptacle is near your darkroom sink.
Many such projects were actually made, some of them are better documented then others. For this application I wanted something that is as off the shelf as possible.
If you buy something like the Sonoff S31 they have an 8266 in them that can be easily flashed