There were dozens of pretty complex challenges, too many to describe here. So just a few examples. First of all, I'm fully bare-metal, with no ESP-IDF (though I use it for studying). A major annoyance is the USB-JTAG flapping which is the same on both board copies and different hosts; so debugging is even more difficult; partly worked around by logging via additional TTL UART connection. It's worse right after power-on and after EN pulses, then stabilizes for ~tens of minutes; could be thermal/supply settling, or simply the burst of re-enumerations any reset causes. Then the LT8912B I2C is shared with HDMI DDC; a lot of time went to find the right drive strength so the LT inits with the cable is in. Also a couple of rev v1.0 silicon issues, e.g two-step cache writeback, dead GPSPI clock, etc. For the display, the Olimex demo was very helpful; dumping all DSI/bridge/GDMA/clock registers over JTAG became an important debugging tool. Now the SD card and display work more or less. Right now, I'm really struggling with the USB keyboard, which is a low-speed device behind the onboard FE1.1s hub; both ways of reaching it fail identically with a bare chhltd and no cause bit.