No, it is not. It is not a modification of C212. N 219 is made from clean sheet, it is what Indonesian Aerospace official said and it is why the look is quite different. Not only the look but also dimension, length, and height is different. If it is a modification then Indonesian Aerospace has to said it as a modification publicly like what he said about N245 program.
The reason they make it from clean sheet is to give experience for the young generation engineers. During early development around 2008, majority of company designers are young engineers that dont have design experience yet. So N 219 program is essential to transfer design knowledge from senior engineers who are about to retire into junior ones.
This is also why the development took quite long, although money is also another problem of why it took the development so long. I still remember when I read a publication talking about the history of the plane, Indonesian aerospace official said every one senior engineer (designer) will be accompanied with 4 junior engineers during the design process.
Many senior engineers left Indonesian Aerospace because of the company get financial difficulties due to IMF prohibition for the government to finance 2 ambitious program (N250 and N2130), this is why there are around 200 Indonesian engineers working in Boeing and others, while some of them are called to help KFX/IFX program.
The one that could be said as modification is N 245, which is a modification of CN 235 by eliminating ramp door and several adjustment on the design. Indonesian Aerospace official also said N 245 is a modification of CN 235, while they dont talk like that about N 219.
Many westerners try to play down Indonesian achievement and some guys here in PDF buy that, even you also buy that.
C 212-400
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N 219
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Cessna Sky Courier (just has maiden flight in 2020)
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They are all 19 seats class passenger plane.