Yes but many inspectors and insurance companies won’t want you

…why would anyone care what those people want?

if there’s something that has the potential to start a fire, you need to have safety certifications

No you don’t.

If your solar system is off-grid AND off-building, I see no reason that you need to have a UL listed system.

You’re missing the point. Nothing is stopping anyone from installing off-grid inverters (or any inverter at all) in an on-grid system.

I would probably be suspect of their products’ quality

Have you ever looked at “top sellers” on Amazon? Most people do not care about quality, they just buy the cheapest shit possible.

These things are not the same, and it’s concerning that you can’t see the difference.

I see the difference, I just don’t care. It’s concerning that you can’t see the potential for exploitation, both from corporations and governments.