⏰ In A Nutshell
You can enable "Use The Built-in Speaker" feature to use an earphone or a bluetooth speaker.
⏰ To Elaborate
Move to [Settings tab > Volume and Sound] and enable/disable "Use The Built-in Speaker" feature.
- If turned ON: The alarm sound will come out via the speaker of your device even if an earphone/headphone or a bluetooth speaker is connected.
- If turned OFF: The alarm sound will come out via the connected earphone/headphone or bluetooth speaker.