Thanks for the pics, morphius2036. I've been looking for teardown shots, yours are the best I've found so far.
Looks like there are three low-profile headers (near the cut-outs in the board),at least two of which appear to have been covered in Kapton tape ... and thus never used during production build/testing
... which suggests that maybe they have an engineering use... ???
Dunno, I've only used Xilinx jtag. Might be a custom pinout, but even ARM-20 pins would certainly fit in that 24-pin connector.