How do i unlink a device from my iCloud

Hi, it depends on how you want to do this:

1. If on Mac OS (Big Sur in my instance), go to the Apple menu > System Preferences > Apple ID and on the lefthand pane, look for the device in question. Press on the device in question and on the righthand pane, there is a Remove option.
2. On IOS devices, go into Settings > Apple ID > and scroll down to the devices part, go into the one in question and therein should be red Remove from account option.

I hope this helps.