You might have noticed in iOS 14 that you can set your iPhone to be more attentive to when you go to sleep and when you wake, and let it try to help you stay consistent by setting a regular alarm for you. These improvements in the Health app’s Sleep section build on previous sleep tracking and wake-up alarms, but add more nuance. This replaces the previous Bedtime feature.
The best place to start now is in the Health app. Tap the Sleep section in Summary (or use Browse to find Sleep settings), tap Sleep Schedule, and then tap the switch. Now you can set parameters, though iOS may suggest them. You can tap Edit Schedule to choose a custom sleep/wake schedule by day or tap Add Schedule for Other Days to create one for days not covered by your existing schedules.