I'm slowly working to start a solar-install company — your post helps confirm my belief that offering a private no-internet option... is a worthwhile differentiator. I have a lot to learn, but the Sol-Ark inverter or Outback (Radian) inverter might be the way to go. Otherwise, it might have to be some obscure inverter without reliable warranty.
Here's a related forum thread: https://diysolarforum.com/threads/sol-ark-needs-a-serious-ch...