So I setup Ampere app, enabled "ignore battery health" settings (or it was not working).
Tested 1 classic 5v 2A charger : 1500mA charging current
Tested samsung 5v 2A / 9v 1,67A : 1500 mA charging current
Tested a dell laptop adapter 5v 3A / 9v 3A / 15v 3A / 20v 3.25 A : 3800 mA charging current
I do not see the input voltage with ampere, if you have other suggestions.
For comparison, installed ampere app on my samsung s21, using the samsung 5v 9v charger, it shows 2900mA charging current, almost 2x more the pixel can draw ...