have you configured your AudioSession with

AudioSession.configureAudio

? by default, the preferred output is still speaker, so if you want the default to output to the earpiece, you'll need to set that.

force_speaker

is only for overriding all audio routes (regardless of whether headphones/bluetooth is connected). You may also want to check out

AudioSession.showAudioRoutePicker

expect behavior is • I can switch between speaker and earpiece