My brand new S21 5G and my S10e don't work properly with Anker chargers.
This is partially Anker's fault and partially Samsung's.
Firstly Anker chargers such as the Nano II range use PowerIQ3 use banned proprietary charging modes that are unsupported by USB-C. This is instead of supporting USB-PD as they should be according to the spec. Their PowerIQ3 technology cycles between PD, QC 3.0/2.0, Samsung, and Apple modes in an attempt to fool older phones to work with it. This doesn't actually work.
Samsung also does something similar. My two phones negotiate PD first, but the phone decides to check the D+ and D- lines for a proprietary charging method, and that causes the Anker charger's cycling method to drop out of USB PD mode.
When the power brick and the phone implement multiple proprietary charging modes in addition to USB-PD everything goes wrong. Using a USB tester, you can see the charger negotiates USB-PD first and charges at full speed. However, after a few seconds, the phone decides to check the D+ and D- lines for a proprietary charging method, and that causes the Anker charger's cycling method to mess up.
Proprietary methods were disallowed in the USB-C spec for this very reason. If the Anker charger simply stuck with the spec and implement USB Type-C current, USB PD, and USB BC 1.2, you'd get consistent and correct behaviour all of the time and not have to wait hours for your phone to charge.
USB PD should always win but the way the complicated proprietary charging mode switching Anker have built into these chargers you end up losing out.
This combination stops USB-PD and drops down to a much slower mode which it can't get out of. The fast charging possible with Samsung's software changes is about 5x slower than it would be if USB-PD were implemented properly.
Is there any way to prevent Samsung phones from falling back to slower protocols? Is there any way to force Samsung phones to stay in USB-PD mode with USB-PD capable chargers?