Use it as a giant iPod (music machine)I think it's a pitty to throw away my Imac
That iMac, no doubt, has served you well but it is now an ancient piece of machinery that won't run any recent (and secure) version of macOS. If you really wanted to keep it around, you could go down the route of installing Linux on it or something.
But in lieu of all that, you might want to take it down to your local recycling place and have them safely recycle the machine.
Are you sure you're looking at M1 16" MacBook Pro's?... I see there are some second-hand 2020 macbook pro 16 with 32 GO and 1T SSD for around 1 369$...