Relays on Unipi 1 are ware wired via I2C gpio expansion so you will needsomething a bit more complicated. There are many options:
linux like https://github.com/Peekayy/mcp230xx Python using already made library like https://github.com/adafruit/Adafruit_CircuitPython_MCP230xx C/C++ or anything else the same way just like Python ...