After a system crash the SBC didn't boot up and I had to install a new version of Armbian from scratch, which brought a new problem: the libraries my software depended on were outdated and I had to rewrite the software using libgpio. It was a good thing, because in the meantime I got a Home Assistant setup up and running, so I decided to ditch the crappy web interface and use MQTT for sending commands and status updates. After some fighting I got it to run like I wanted - here's the code: https://github.com/keriszafir/hifipower