I can't answer as to whether an AT&T port would be usable, but I do see where other sites are selling the ports specific to the carrier. In your case the model number of your Note 5 would be SM-N920P, and searching for a charging port using that number returns several specific results that are for that Note 5 and not others.
[link|https://www.ebay.com/itm/284887000654|NEW OEM Charging Port Mic Flex For Samsung Galaxy Note 5 N920 All Models|new_window=true]
[link|https://repairpartsusa.com/products/samsung-galaxy-note-5-dock-connector-flex-cable-sprint-920p|Samsung :: Note Repair Parts :: Samsung Note 5 Parts :: Samsung Galaxy Note 5 Charger Dock Connector Flex Cable - Sprint(920P)|new_window=true]
[link|https://www.amazon.com/ePartSolution-Replacement-Samsung-Charging-Connector/dp/B0B48B7XCR|Amazon.com: ePartSolution Replacement for Samsung Galaxy Note 5 SM-N920 USB Charger Charging Port Micro Dock Connector USB Port Flex Cable USA (N920P (Sprint)) : Cell Phones & Accessories|new_window=true]
My suspicion is the ports are particular to the carrier for some reason, so I'd suggest sticking with the original carrier.