There are a bunch of strategies here, but one people oft repeat is the "buy, borrow, die" approach. Where, they are kicking the can down the road, but the magic happens at the die step. When the borrower dies:

Your heirs inherit your stocks, with their cost basis reset to the current price. This means that they have zero appreciation of your purchase of $RIVN at $67, despite it being at $420. They can then sell the shares, to pay the loans, and not owe capital gains, because there are no gains. Additionally, at this step cash can be extracted for no gains as well if desired.

So you avoid taxes while alive by taking loans (not income), avoiding capital gains (never selling), and then gains evaporate through a stepped up basis. There are some exceptions here - estate taxes, etc with ways around them like trusts, but this is the general mechanism.

Its worth noting though, that its not ironclad. In a significant downturn you can be forced to liquidate and it will hurt (see the news on Musk right after X purchase). Additionally, while people talk about this as being super popular, realize that in practice people who take advantage of these strategies also still have millions in cash flow, so its not a true borrow only $0 tax lifestyle, they will use already taxed money to manage them as well.