Hello MrKa0z,
Thanks for using Apple Support Communities! We see you're having an issue with your M1 iMac and Touch ID with a Magic Keyboard, and we'd like to help.
Were you able to follow all of the steps in the article viewed, including powering the Magic Keyboard off/on?
If Touch ID isn't working on your Mac
If so, and you're still not able to find the Touch ID in System Preferences, let's try some other troubleshooting steps:
Start up in safe mode. It may take longer to finish the start up, as safe mode does some system checks, and can sometimes resolve unexpected issues. You'll also see some differences in the display. This is expected with safe mode, and when you restart normally, they'll be gone. Restart normally, and test again.
How to use safe mode on your Mac
Test with a different user. If you doin't have another user set up, here's how:
Log out, sleep, wake, restart, or shut down your Mac
Take care!