See this. Perhaps soldering in the same way a connector on the IOMCU JTAG port you can read the firmware.
BTW, if you are making a new board, I have always wondered why servo signals have 3.3V levels: connecting the TXB0108’s to some internal 5V supply would solve WS2812 voltage levels incompatibility mentioned here and there.
So not knowing if there is a reason, perhaps some kind of soldering jumper to choose supply to those ic’s would be a good option.