How to Troubleshoot Acer Laptop Not Powering On

I have a 2020 Acer Nitro 5 AN517-51-75X3. It doesn't show many signs of life and I've met a dead end in troubleshooting. Does anyone have any idea how to proceed?

This is what I observe

• If I plug in the charger, the blue battery light is stable
• Absolutely nothing happens when pressing the power button: no fans, no lights, no beeps, nothing

I am comfortable with a screwdriver and own an Ifixit pro toolkit so I can get pretty much anywhere, but I have not been able to find any schematics online for this motherboard, and although all ports are labeled, most labels are just some letters and numbers, and not actually informative. Acer and their service partners probably have a list for that, but I wasn't able to find it online, so I'm flying partially blind.

I have tried these things:

There are no peripherals connected to the laptop.

• hold the power button for 10, 25, 30, 60 seconds as well as a lot more times for different durations
• remove battery and charger, hold power button for 90 seconds to drain residual energy
• use a multimeter to confirm the battery delivers power (~16.8V, should be anywhere between 14.5 and 17.9v, so that's fine)
• use a multimeter to confirm the charger delivers the appropriate voltage to the motherboard (measured behind the thing where the power socket wire connects to the motherboard)
• use a multimeter to confirm the keyboard connector has power to ground at least at several pins
• use a multimeter to verify the CMOS battery delivers charge (~3v)
• reseat RAM
• reseat a lot of other connectors
• visually inspect entire motherboard, there are no signs of damage to the motherboard, capacitors, or anywhere else.
• short the 1&2 pins on the keyboard connector to ground (separately) to try and force a boot

Nothing I try seems to make any discernable difference to the laptop behaviour.

This is what I'm looking for

I would like some pointers on what else I can test or verify to try and pinpoint the issue. Currently my only remaining guesses are

1) the keyboard is non-functional, and since that contains the on/off button, the laptop can't turn on because of it.

2) the motherboard is toast, but I consider this unlikely because 1) it's never the motherboard and 2) there are no visible burns, leakages or damages anywhere

Does anybody have an idea on:

• how I could eliminate or confirm the keyboard as a cause (preferably without having to buy a new keyboard because those are expensive for a test),
• how I could test/eliminate/confirm the motherboard as a cause
• what other things I could test

Thanks in advance!