The early ones had all the chain issues. By 2013 that isn’t much of an issue. They need their oil changes, I’ve seen a few neglected ones have the cam actuators go bad from being starved of oil. The most common issue tends to be leaking purge valves, and they’re easy to do.
I own a 2015 Impala, or course I keep the fluids fresh in it but it’s been a very nice car with 78k on it now. My parents have a 2016 Impala. I’ve worked on many of these and know them well and wouldn’t have bought them if I thought they’d be a money pit.
Even the early ones can be a good buy if they’ve had the chains fixed. The engine is typically mated to the fwd 6 speed which can have issues too. Better parts were used about the same time they got the chains updated. Typically more of an issue in the Traverse/Acadia platform due to hauling more weight.
This is not to be confused with the second generation 3.6 which started production in 2017, however they still use both. Haven’t seen much out of those but it’s early yet. Just a few solenoid issues for the cylinder deactivation, and yea that’s how you can tell, the second gen shuts down 2 cylinders.