I think the methods you mentioned are very good, and they almost cover all the ways I can think of using Bitcoin to make money. In 2021, I am more inclined to airdrop this way. Of course, if it were in 2010, I would definitely choose to invest or mine. This would be a way for me to reap a lot of wealth at almost no cost. But now, I don’t have enough money to buy Bitcoin and use it as an investment method. Of course, if the price of bitcoin continues to fall, I think I will still buy some bitcoin at a low price, and then wait for its price to rise.