I've talked with some people who are UHNW and some of them are seriously considering such strategies.

As I mentioned in another response, you can invest through, e.g., direct indexing say in NASDAQ 100 companies. The average dividend yield is 0.75%, so your portfolio would throw off $75k. I'm sure that a good accountant could find enough deductions to reduce the taxes owed to next to nothing.

I'm no accountant, but you'd be able to deduct mortgage interest on up to $750k. If the mortgage interest is 5%, that's aleady halfway there - $37.5k. Add $37.5k annual charitable donations (e.g., via a donor-advised fund), and your taxable income drops to zero.