An Issue with Normals and SubDivison A visible seam is observable during SubD operations on a boolean cut.
Prior to applying the Boolean I created supporting edge loops which are not approximately* in line, they are exactly* in line, ie. mesh topology looks so good it brings a tear to the eye.
Despite this, for the past 2 weeks this issue persists. Weighted normals and proximity loops help the overall shape, but only minimize this particular effect. A blend file should be attached. Picture illustrates issues.




Is anyone able to identify this issue, and what the solution is?
Merge by distance M&gt;B and change the threshold until you've removed enough vertices to minimize the seam.
Then add an edge loop to support the geometry in front of that area.
See the gif below for a visual:


Note that this will fix the issue for now, but in the future, you should consider better topology, and not strictly rely on booleans for modeling.
topology guides is a good resource to begin with, and there are many questions here on the site that will lead in the right direction also.