Flashing D3 Kernel on a Tx2i

This is your problem:

I also did not see anything for EDID or accepted modes or mode pool in the Xorg log. So far as the driver is concerned, there is no monitor connected (or perhaps no driver capable of reading EDID).

EDID is mandatory for the driver to set a mode. In turn, EDID uses the i2c protocol, and if i2c is missing or misconfigured, then there will be no EDID. Different carrier boards will route certain controllers and wiring differently, and it is possible that if you did not have the correct board support package installed, then i2c will fail and then EDID will fail. If the monitor is not truly HDMI, then this too could cause such an issue, but generally speaking it seems odd to see no mention at all in certain logs. I suspect that if you follow the information from @D3_growe it will get i2c working, and then EDID and finally the correct monitor config.