This one crossed our mind as well, the problem is you usually don't compete against billionaires but rather against corporations or conglomerate which has much more economic power that single individuals. You also have to account for the benefits that these private entities can promise (knowing a law will favor a certain industry is a good way to make cash by buying stocks before said law passes), that's quite hard to compete with that when you're a philanthropist

Decipher Security for a heavy infosec focus

Technology Pill by Privacy International for something looking more at the impact of tech on society and human rights

And as other have said I do enjoy the occasional Linux unplugged!

Pesticideless farming that's respectful of the environment, easy way to make people healthier without damaging the plant further and while thinking about the future sustainably. Sounds like a decent deal to me!