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T2 possibly damaged by overvoltage through its data lines connected to audio board. Check diode mode to ground at SPKRAMP_RESET_L and SPKRAMP_INT_L.

Did you check diode mode readings on all coils, including L9080?

"How do I see if it is recognized as 140W? ............................... You can test with a working MacBook, if the charger is recognized as being 140W" It is listed on System Report. You should get a battery holding some charge, for proper test. Trackpad haptic is not a signal of booted board.

USBC meter is very useful; it shows if charger switches to 20V and the current consumption of the board. Discard 87W charger, is not good for this board. The charger cable is also important, as for 100W (or more) the cable must be electronically marked. You can test with a working MacBook, if...

Once F7000 is removed, which side remains 0.087 reading?

Any history available? Be aware, if battery is empty, or not connected, this board requires 96/140W charger to turn on.

L7800 (A2337) has the same specifications as L8430 (A2681). Seems that you have more problems on the board; maybe U8100.

PCH, CPU, BIOS. Just in case, try known good BIOS.

Any secondary coil gets similar reading to ground in diode mode (close to 0.087)? Remove F7000 and check C7050 voltage.

Any history available? Check LED return resistors and their traces. Compare diode mode readings around U9701 with good board.

I don't have proper dumps for this model. All the files I got from vinafix, seem to be bulshit. Specify which CD3215 chips stay at 5V. Compare diode mode readings around all them.

"Don't have another A2681 board" Even M1 boards have 5V boost line.

CPU core should drop to 0.6-0.85V, when machine boots.

Do you get image for sure?

Not sure if this board accepts GPU disable like in older models (3787). Tried safe mode?

Check again U7000 voltages with both charger and battery (holding charge) connected. Let see if all voltages are stable now.

Is your board 00163, or 00138?

All USBC ports have the same behavior? Test them flipping charger cable also.

Maybe CPU/GPU problems...

S5 voltages appear later in the power on sequence. G3S and SSD voltages must come on before that. You can try DFU with external switch method: https://logi.wiki/index.php/DFU_Mode_Restore_(Macs)#DFU_Mode_using_external_switch