If your phone does not have any resale value, you might enjoy taking your smartphone apart to see how it all works (in a very crude and functional way…oh! this is the RAM…oh! this is the gyroscope chip…and this is the WiFi receiver). This is especially fun if you have kids (or are a kid, physically or mentally), and doing it on an old phone will give you the confidence to switch out individual parts on your new phone if they fail.
I recently took apart my old Samsung Captivate (the last phone with a physical retractable keyboard that Samsung made) and now I am obsessed with teardowns. All acquaintances should hide their old phones.