Unbrick Asus RT-AC68U router over serial connection using a Raspberry Pi

I recently did an RMerlin upgrade and botched it. I can`t say for sure how but likely not resetting the router properly and unplugging the unit at a critical point. Tried the firmware recovery, setting IP on computer and holding reset. Twice, recovery loaded to about 80% then pooched. After a third try, recovery didn't even find the router anymore. No ping response either when start router normally or when go to recovery mode.

I tried wireshark and while I can't pretend to know even...

Unbrick Asus RT-AC68U router over serial connection using a Raspberry Pi