I have faced something similar as well. I have the same droning sound while uphill and it becomes quiet once it levels.I noticed the same issue yesterday on mine. Uphill under load it sounded similar to an Jetta TDI. Once the road leveled out it was all good.
The engine is usually really quiet under normal driving. Maybe we just are not used to the smaller turbo engine noise while under load. have driven 1400 miles as of now.
I also owned the 2020 Sonata(which i think shares the same 1.6T engine) and it did not have that issue btw.