Well that doesn’t seem like good news. Maybe trying netinstall, and/or using different form of power (e.g. use PoE if you were using the 5.5/2.1 jack, or vise versa).
There are pad inside, but never messed with them. If netinstall didn’t work, kinda tells you getting serial port from pads may not help since it both need RouterBOOT to work.
From what I read production RouterBOOT does not have the serial console enabled for devices that have internal pads.
Netinstall would fail even if the damage was limited to the Ethernet ports. The inability to do a reset and get access to a default SSID is more telling of a complete meltdown.