Hyun/Kia is very polarizing on this board. It’s unlikely that you’ll get much more than anecdotal evidence. The thing to know about Hyun/Kia: the 2.4L were not great engines. That said, the vast majority of them produced went well beyond their generous warranty. The other engines are generally solid. Decent power, good fuel economy, maybe a bit unrefined, but not terrible. The most important thing, in my opinion, is maintenance. I don’t think these engines take neglect well. Good maintenance will help a lot.
Anecdotal evidence time: 79k on my Elantra, no issues, no oil useage, 40 mpg on the highway.