Executing Edit Alarm
in Shortcuts stops the current alarm and opens the 'Alarm' section of the Clock.app .
Obviously not a solution that runs completely in the background.
Currently I cannot confirm how it behaves on a password protected device.
Can you elaborate a bit more what you seek to achieve?
Perhaps it is more feasible to create an Automation/Shortcut that rings an alarm sound at a given time for n times and then stops.