ответ 2

1.First off, that mesh is not going to look good regardless of how you terminate those edges.

The distance between segments is uneven, so the cylinder isn't even round.

2.First off you need to get a proper round cylinder in there.
Second you need to make sure that the number of segments in the cylinder works to support the box-cylinder boolean.

cylinder #3 clearly has more segments than #2, but you see that in both cases the sides of the box has the same distance to the outer cylinder segments.

3.General rant (Sorry Jordan):
You can't just dump polygons on a problem. When me and Joe started saying "more polies", that's not what we meant. I kind of regret that whole thing now because we see a lot of people who apply the idea poorly, going way beyond our intentions, using insane amounts of geometry where other solutions would have worked far better.

Yes, it's a common problem that people use too little geometry and then don't understand why the shading looks bad, but there's theory behind it. You can't just add lots of geometry and hope for the best, it's about understanding how the bad shading happens in the first place, understanding how subdivision works.

The key is the angle between adjacent geometry and the distance between vertices.

Since vertex normals (ties directly in with subdivision) are dumbly averaged, shading (and geometry position/angle in the case of subdivision) bleeds into neighboring geometry. By terminating with a loop, you can "dam up" the problem, essentially making it less visible because you reduce vertex distance - however, this means creating a hard edge, which you won't want in the case of working with cylinders and the like.
So with a cylinder, or any curved geometry, you need to make sure that the surrounding geometry supports the cylinder, not the other way around.
You can often get around that challenge by increasing the polygon density of your curved meshes, and often you can do that dumbly, but you're much better off understanding the cause of the problem and giving it the exact correct solution for your specific case, and end up with less geometry, and cleaner at that.

cryrid, not to pick on you or anything, just using this as an example, I'll remove it if you want:

This picture shows just following the "more geo" mantra blindly without understanding the theory behind it.

You know, 48 sides is pretty insane, and more than that? No, what you want is to reduce the number of sides, just make sure they line up as best as possible with the surrounding geometry, and/or terminate the two loops in question somewhere else. You have really terrible shading problems there, regardless of all the geometry you used. The simplest cylinder I made above uses 16 sides and works 100% perfectly for the cylinder end.

That mesh has the same problem as the original: Uneven distance between the cylinder segments. You should never do that. The only cases you can get away with it is when the position compensates (But that's an "advanced" topic) or when the curvature is gentle enough that the shading errors won't be very visible (I've done that a lot on spaceship panels and the like)

Also, just a small thing: There's a couple different ways of connecting boxes. They both have their uses