I have the exact same issue on my S6. I can no longer fast charge or even normal chargevvia cable, can only get a super slow trickle charge. I have tried several cables and several chargers that all work elsewhere but no longer on my S6.
I can still normal charge or fast charge using charge pads. But i am mobile most of the time and need to fast charge while driving and using a Samsung fast charge battery pack or fast charge car charger.
Since the life of my non changable battery has worn down from most of the workday to half of tge workday, this is a serioous limitation on a phone that should be at worst its halflife and still have a year of payment remaining.
I also found out that there is a problem getting files off of my non removable built in storage via usb cable. Another major blow as i use that frequently. I had to resort to using a tedious ftp server that works over wifi and is very ineffiecient to use.
I tried all the hints in the forum, no luck. Anyone have a diagnosis (software upgrade issue needs,a fix?) or very invasive risky usb port replacement, or ??.