My Bluetooth speaker switched to Chinese after a few years of use. I have no idea of how it did it and no idea of how to revert it. There is no reference to it in the manuals.
A few days before, I brought a robot vacuum home. It was made and purchased in China. When I started it for the first time, it bumped into my server and unplugged it.
Therefore a state-sponsored cyberattack is not out of the question.
I have a pair of Bluetooth headphones that indexes through 3 languages (Mandarin, Korean, English) on startup when you also hold down some other button besides power (play/pause IIRC). I don't think it's documented. Maybe your speaker is similar.
A few days before, I brought a robot vacuum home. It was made and purchased in China. When I started it for the first time, it bumped into my server and unplugged it.
Therefore a state-sponsored cyberattack is not out of the question.