In order to use non-Tesla DC fast chargers from networks such as Electrify America, EVgo, or ChargePoint, your older Model 3 (before Oct 2020 with chrome trim) will still need to have CCS enabled regardless if the plug is NACS/J3400 or CCS1. Purchase a used Gen4 ECU p/n 1537264-00-B or 1537264-01-B from eBay or similiar for as little as $75 or buy new on EPC (Tesla's parts catalog) for $140. Purchase "A Bundle of Wires with a Board" less than $65 here . Remove your older Gen