Going to the basic steps.
The nozzle is clear, since you have no trouble pushing it by hand.
The temp is close enough.
With a clear nozzle and proper temps, that means the extruder is likely to blame.
The physically weakest part of the extrusion system is the small herringbone gear on the motor, then the motor itself. I’ve also had a stepper motor on the single extruder go out, and replaced a couple of those small gears.
I’m guessing you have another NEMA17 to swap in there? And using one of your other printers to print up a new small herringbone gear to put on it is definitely worth a shot.
Beyond that, it could be the stepper driver, which you can test around by using a firmware build that uses the second extruder stepper driver for the first extruder. I’ve got a build of the firmware that swaps extruder drivers here: Incorrect Extruder stepper motor wiring killed my Rambo? - #5 by Wrathernaut
Just flash that firmware and swap the plugs for E0 and E1 at the control board.