Avoid adding loops that break up the even spacing around a cylinder. You can try leaving an n-gon which probably is good enough or remaking the cylinder with more loops around it.
How should I resolve this geometry to avoid pinching after smoothing? I can't seem to figiure out where should I put additional edge loops without ruining the shape of the object. Probably would've been just faster to dynamesh it in zbrush and boolean the hole, but I'd like to understand what to do in this situation…
Also, while not providing enough segments for that performation too display as expected once sub-d is enabled, shading artifacts are likely to occur because it's algorithum can only perform predictably upon what one happens to dish up. A good rule of thumb is firstly figure out how many cylinder control loops will support…