Looking at the image again, though, there are several other potential candidates.
It's straightforward enough to check out.
Take your USB to TTL serial convertor, attach the GND wire to any of the big corner holes that the mounting screws go in - or the metal plate they connect to if the board is still assembled.
Wrap the RX wire around a short needle and start up PuTTY or your favourite serial terminal program, with likely settings 115,200 baud rate, 8 bits no parity, no flow control.
With the camera powered off, poke the needle gently on to one of the pads marked TP around the big SoC chip in the middle.
Power on the camera and watch for readable text scrolling up in the terminal. It will likely finish with a '#' prompt, it might be static, it might still keep scrolling.
If nothing, power off, move to the next pad and power on again.
When you've got the right one, you need to get another hand to keep the Return key pressed on the keyboard.
Wrap the TX wire around another needle and whilst keeping the original needle in place, probe the pads marked TP and look for the one that generates new lines on the terminal screen. The return key will be sending data if it's kept pressed.
When you've found them - the hard task is then to fix the wires in place so you can make use of the access.
But be careful - don't short things out.
