I own two Ender3 printers, a stock one and one upgraded with SKR mini E3 v1.2 and BMG clone.
I calibrated the E-steps using the filament measurement method ~415 looks correct.
The machine severely over extrudes, reducing the flow rate to ~50 % looks right. I would say it pushes out about twice as much material then it should.
I am testing this using a simple one walled cube, sliced with Cura 4.7.1.
Printing this will have the wall thickens about double and several blobbing on the side the layers are restarted.
Printing the same G-code on the stock printer works without problems.
Printing from the card or using Repetier Server does not make any difference.