The model is a modified cylinder by moving some of its faces upward along Z axis. It has a shading issue shown on the following screenshot. How to fix this please?
The following screenshots are what I see after checking the solution from KISKAart, who proposed to use knife tool to break the N-gon into quads, so that the shading issue could be fixed in a way.
However, the knife cuts and additional loop cuts cause new shading problems: