I have the problem, that when I plug in a headphone jack, while sound does start on the headphones it still continues through the laptop speakers. When I check in the sound settings, it only shows one output device.
When I connect my headphones via Bluetooth, the sound switches automatically to the new output device.
I am still new to this OS so apologies if this a stupid question.
I had this issue once, then I realized that I plugged my headphones to the microphone jack, because headphones and microphone jacks are close to each other, so check if you plugged to the wrong jack.
Ohh and there is only one audio jack on the laptop. So I don't think that is the problem. (I did build a PC before and wondered why the screen was not working only to realise after two hours of troubleshooting that I plugged it in the motherboard and not the GPU xD)