So one of my bixby routine is called Sleeping. This routine turns power saving mode everytime my phone detects that i'm asleep. I set an alarm to wake up early in the morning, to my surprise the alarm didn't ring when it was supposed to. I gingerly investigated only to discover that when power saving mode was turned on, the clock app was deactivated. Thank God I didn't miss my flight otherwise I wouldn't trust my device again !!!
That's why it is recommended to have a separate physical Alarm Clock. You can also use a second phone (old one that you may have sitting around somewhere) as Alarm (which I do). Now you won't have any trust issues with your daily driver phone.