So I have an L390 Yoga with USB-C charging. Original adapter works at full speed. I got a 45W power bank, works at full speed.

But that was just a coincidence.

I already tried 5 other adapters and all can only charge it at 10W with 5V. 3 were 22.5W, so maybe, but now I got a 45W GaN adapter, with the same 20V 2.25A as the power bank, yet again just 10W. It even has PPS.
I also tried a 66W adapter I have, with 20V 3.25A mode, 10W again.

The only 3rd party thing that works is Choetech B653 power bank.

I have also tried 2 different cables, one of which is rated at 120W, but both only work with the power bank.

So what am I missing? Or is it just some Lenovo BS to make you use official adapter?

Like this it’s faster to charge the power bank, and then the laptop from it.

Edit: Switches to 20V when I connect something to USB-A on the adapter, but keeps turning off and on repeatedly (the adapter).