I thought it was the timing chain guides more so than the metal chain itself.
Replace your timing chain at the correct intervals.
When did G.M correct this issue, or did they just ignore it and let the customer deal with it?
The timing chain issues of the 3.6L are in the past from at least 2013 and up. There will still be some outliers, but overall, they don’t have the same issue anymore. Timing chains don’t have an expiration date like timing belts. The best thing you can do is keep up on oil changes. If the timing chain guides wear out, the tensioner fails, or the front engine cover needs to be resealed, I would recommend replacing the timing chains and components during the process. If you have a high mileage motor (75k and above), otherwise stay up on oil changes, check your oil level at least once a month, and maintain regular maintenance like tune-ups, fluid flushes, and decarbonization. Drive easy, go/easy stop. These things combined will give your vehicle and engine the best chances for longevity.
Use better oil and change your oil more often. There is NOTHING you can do about past neglect, the damage is done.