They could use their money and influence to lobby the government in a positive direction, such as making sure taxes go toward social programs instead of killing brown people, and then simultaneously help fund that by filing their taxes fairly and paying their intended share rather than do this arcane skullfuckery to pay as little as possible. A great next step would be to lobby for tax code reform to close the arcane loopholes (and ofc massively raise taxes on anyone with an income north if $1M/yr) so that other, less charitably minded billionaires can start paying their fair share too, whether they want to or not.

So imagine there exists a charitable billionaire that wants to do good. How in your eyes would a billionaire go about donating their money without drawing this same criticism?

I'd say the answer to that, is that they should simply give significantly more than what they're currently giving. We're talking of people who could easily give away 99% of their wealth with 0 personal sacrifices. If they're giving less than 0.1%¹ instead, I just want to know why?

I found this webpage extremely helpful for putting into perspective just how much good they could be doing: https://mkorostoff.github.io/1-pixel-wealth/

¹) That number probably needs to be a lot smaller, but I don't want to make any claims.