This kind of effect is similar to the popular non-mainstream, but not so exaggerated, abandoning photography or some specific constraints in post-production!
I haven’t written anything for a long time, mainly because there are few similar tutorials on gradient mapping on the Internet, so I simply wrote one for discussion and exchange.
Effect 1 is the final effect of this tutorial
Effect 2 is to flexibly use gradients to map the foreground and background colors.
Effect 1