Works exactly the same as on One UI V4.1 on my S20 Ultra One UI V5.0.
Check to see if you have any apps set up to Ignore DND.
My DND works perfectly, turns on & off at exactly the set times.
If you didn't Factory Reset after the One UI V5.0 update, then do that. Backup with Smart Switch FIRST ⚠️
It looks like
Bedtime mode moved to Bixby Routines
You can now manage Bedtime mode in Bixby Routines instead of Clock. Bixby Routines lets you automate more actions when it’s time for bed, like turning on Do not disturb or changing other settings on your phone.
Choose modes based on your activity
Choose a mode based on what you’re doing, such as exercising, studying, or working, then choose what you want your phone to do in each situation. For example, turn on Do not disturb when you’re going to bed or play music when you’re exercising.
Hi, we recommend you to back up and factory reset the device and check again.
Please visit the links given below and follow the steps to perform backup and factory reset.