PC won't turn on, no lights.

Since this morning, my 2016 ACER laptop won't turn on.
I began to turn it on as usual, not paying attention to its reaction, expecting it to turn on normally.

However, after some time, the black screen intrigued me. I realized that no indicator light was on. So I pressed the power button again, still nothing.
I then tried unplugging my USB peripherals, plugging in the power supply. Still nothing (not even a light indicating charging).

I noticed that the laptop's fan was running faintly, but nothing happened, no lights and no reaction.
However, another problem: it won't turn off anymore. No matter how long I press the power button, for 10, 20, or 120 seconds, nothing. I've "turned it on," so to speak, and it won't turn off.
Note that the battery cannot be removed from this laptop, so my only option is to take it apart to see what's wrong, but I'm afraid to do so while it's "on." Waiting for the battery to drain with the screen off and no activity is going to take forever.
The only unusual thing that happened recently was that it took a long time to shut down the last time I used it.
I'm worried it might be the motherboard, given that the indicator lights are off, but on the other hand, the fan is running...

Thank you for your time, any ideas would be welcome :D