How do I remove an alarm on an iPhone 8

Go to the clock app, then swipe left on the alarm you want to delete, then press delete.

Or, press edit in the top left corner, then press the minus button, and then delete button.

Or, press edit, then select the alarm, then press delete which is at the bottom of the menu.

btw this is for IOS 14, I don't remember if it's the same on IOS 13 and earlier.

That depends on whether it is an alarm you set through the Clock app or through Health. The directions given above are for removing one set in the Clock app.

To remove one set in Health, open Health, go to Sleep. Tap "Full Schedule and Options". Tap "Edit" for the alarm you want to remove. The tap "Delete Schedule" at the very bottom of the screen.