Fast forward.... I have the same problem on my Galaxy S21 and it's a HUGE problem. If I'm concentrating on a phone call I don't even hear those 2 or 3 very tiny and low beeps! This is a disaster. I live by my many alarms and I'm often on the phone when they go off. What is Samsung thinking? That's why you give the user so much choice on other things, but here you've decided what's right for me and I can't change it.
In Phone app, I have Allow alarm/notification sounds in calls turned ON
In Clock app, I have a custom tune selected.
Under Notifications, I have Upcoming Alarms turned ON, Alert ON & Show as pop-up ON. Alarm and timer alerts is OFF (grayed out) by default (unable to turn this on), which seems inappropriate.
I've spent hours with Verizon & Samsung trying to figure out why I only get those 2 low beeps instead of my custom Alarm sound to ring when I'm on a call. Furthermore, the little pop-up clock that I was able to get to come up is rather useless, because I don't usually see it if I'm concentrating on a call or looking at my monitor AND there's no "x" to close it. The pop-up doesn't go away until you turn off the alarm that just happened, which requires you to turn it back on again if it's a daily alarm (as many of mine are).
If this is not a bug, it sure is a huge design flaw and shortcoming! If there's user flexibility needed anywhere, it's with alarms. No-one wants to miss an alarm!