I've just recently encountered the exact same issue.
An alarm has started going off at loud volume at 7AM every day (Samsung Galaxy A13).
In my case I have had this phone for around 10 months and not installed any apps on it recently so it is mysterious that this has suddenly started.
It seems I have two clock apps installed but neither of them indicate any alarm is set when I open them.
I do see an alarm icon on the top right hand side of my screen so I can imagine that I should expect the same tomorrow unless I can track down the culprit before that!
(Edit: I uninstalled the other clock app. The "Galaxy Store" one has no "uninstall" option. If I "force stop" that galaxy store app clock the alarm icon in the status bar goes away and it comes back if I start the app and go to the (blank) alarms page so I guess this is responsible, it shows no enabled alarms though)
The only significance "7AM" might have is that this is the default end for the "Sleep" schedule so maybe something has got corrupted with that. But it isn't clear to me how to reset this app.
(Edit2: I found the clock app in settings and clicked the ellipsis, and selected "uninstall updates" and it asked me if I wanted to uninstall all updates and restore to factory version. I have done so and now the alarm icon has disappeared from the status bar so I guess that has fixed it!)