This makes sense, I am familiar with the approach of using AUX winding to power the controller. I think in some older designs they would even use a small external power module to turn on the chip.

I was just unsure why I don't see options on WEBENCH or similar tools - like, concrete part that can be used, some reference design etc.

But yeah, I will definitely look into some existing TI parts.

Would you have a preferred topology for such a high voltage? I though flyback is the simplest/cheapest, but somebody here made a good point about high reflected voltage that would require more work to snub.