Since other people seem to be asking the same thing I wondered last summer, I thought to share my DYI solution for a inverter on off switch. I have a EasySolar 24/1600.
Initially I opted for a mechanical switch but since it was hard or impossible (to my knowledge) to have more than one for a single unit it was not satisfactory to me.
So what I did instead was to utilize the MQTT service built in to VenusOS (via Raspberry Pi).
I’m using a esp32 based M5Stack Atom Matrix buttons, that send commands to the main unit via MQTT. I built the firmware for the buttons using ESPHome, which I’ve been successfully using in with Home Assistant prior.
So the pros of this solution is that you can have as many switches as you like, and they are kept in sync (all the buttons shows the status of the inverter), and best of all it was pretty easy and cheap. Obviously there are drawbacks too: they use power (though so little that it doesn’t really matter to me), and you need to wire them to a power source, and they are dependent on local WiFi and a VenusOS, so it’s brittler than a physical button.
All that said, I’ve been using those at my summer cabin now for weeks and they’ve been working solidly.
If someone is interested hearing more, shoot me a message.