Hopefully some original owners with 2017's will answer and you can see what mileage they have reached.
My Stinger is 2019 model and just reached 39,200 with no issues. I always adhere to scheduled maintenance etc.
The Kia brand is very reliable these days, of course you can always get a Lemon in any brand.
Our other car is a Cerato hatch, just a small practical run around, its a 2014 model and done just over 222000kms with no issues at all, it clocks up the kms as my hubby's work is 1.5 hour trip there and back.
No one has a good answer for you here, because the platform simply hasn't been around long enough. Everything in it is new, aside from maybe the engine blocks.
In the four years or so that the Stinger has been around, there haven't been any major common problems that I've seen or heard about. Some possibility of oil consumption as miles rack up over 100k, but that's pretty common for any engine that passes the 100k mark. Transmissions might let go if you decide to push more than stock power, likewise for transfer cases on AWD cars. Stingers with over 100k on the clock are still pretty rare, though, so there's just not enough info to go on.