I've managed to get a bit more info, and I don't think that there's anything to be done from the config and/or code in OpenCamera - looks like it's a result of how Android handles things when the BLE keyboard is connected (also when disconnected). I had noticed that the screen seems to flash and redraw when it is connected, and the same thing happens when running any other app. For reference, here's what I see in adb logcat after the keyboard is connected: 04-29 18:03:05.562 1503 1503 I InputMethodManagerService:...
Just a bit more info: I set up an ESP32 device to behave like a bluetooth HID keyboard and it is behaving the same way: When the device is disconnected and reconnected (ie: by power cycling it), sometimes the camera switches from rear to front (or the converse). Also note that it seems to re-focus the camera. Having a bit of trouble getting ADB to work, but I'll try to get some info from the application side.
Switching to front camera when using Bluetooth remote
VOTE: hydrogen