[Faaak]

Bullshit. All "hybrid" inverters nowadays (grid tied + battery backup), auto island themselves when the grid is out.

That misconception is now 15 years old

[pbmonster]

That system is 5 years old. It feeds electricity back to the grid.

For an "auto island" functionality, I would need relays controlled by the inverter on all 3 phases between the electricity mains and my main switch box, right? I don't have relays like that.