Oddbean new post about login | logout From your description I think you need to clean your charging slot 😛, a lot many phones are discarded because of this single issue when they can be saved so easily.
Charging must have worked. It's at 80% after booting 🤷♂️ Maybe the third Powerbank that I connected did the trick. Honestly don't know ..
next time press the power button to pause the boot for a few mins until battery gets above 3 or 4%