Modern TVs will just switch to the “normal” output when there is no Bluetooth connection.
Your tv has a headphone switch: it is conveniently located in the headphone plug.
You could try to connect your headphone to another audio output (AUX or even a HDMI) an see if that can be manipulated through the menu.
Or maybe when you turn the “normal” audio down the AUX output still gets a signal— you then have to find a different way to control the volume of your headset.
I was surprised they’re still using that old style audio jack.
I need to check for tvs with built-in bluetooth audio. They should have a switch in Setup menu. It may be like android phones. Shutting off bluetooth restores the internal speaker. Or just shutting off my bluetooth speaker restores the built-in speaker.
There is a HDMI jack that I can try. RCA jacks for input. Not output.
I may give this tv to a family member. It’s a Vizio that I bought in Feb. I don’t want to risk a fall standing on a chair and reaching behind this tv to unplug the audio cable. It’s mounted high on the wall.
Virtually every modern tv allows you to turn the internal speakers off and on from the menu, not by plugging in to the audio out.
I have a 10+ year old Samsung with a Bluetooth transmitter plugged into the audio out, but I can still turn the speakers on if I don’t want to wear headphones.
What about getting a sound bar with an audio out jack? It will depend on the audio switching options in the sound bar, but that would be cheaper than a new TV.