Typically not publicly documented if no one from the flight reports or if it was minor and didn't warrant any press coverage.
Looks like it did warrant a mention on AV Herald which is the best place to look for things that don't always receive any press coverage or don't have FlyerTalkers aboard.
A Delta Airlines Airbus A330-300, registration N806NW performing flight DL-30 from Atlanta,GA (USA) to London Heathrow,EN (UK), was enroute at FL390 about 260nm west of St. John's,NL (Canada) when the crew reported smoke in the cockpit and decided to divert to St. John's, the crew requested (and was cleared for) runway 29. While in contact with Gander Center (Canada) the controller reported they have had four or five reports of smoke in the cockpit with Moncton Center, smoke from the Colorado wildfires had gotten into the jet stream and it may be just that for DL-30 too. The crew acknowledged and continued the diversion landing safely in St. John's with emergency services on stand by about 45 minutes after leaving FL390. Emergency services inspected the aircraft and found no trace of fire, heat or smoke.
Incident: Delta A333 near St. John's on Oct 22nd 2020, smoke in cockpit, possibly from wildfires