We saw earlier the definition of "non-avian dinosaur": "Dinosauria minus Aves".
Now let's look at which of these so-called "non-avian dinosaurs" had feathers. We see that only maniraptora had feathers! The others had "decomposed collagenous fibers" - which are so-called "protofeathers" by the dino-to bird enthusiasts but which are just decomposed skin.
"[so-called] protofeathers (thin, filament-like structures) are known from dinosaurs at the base of Coelurosauria, such as compsognathids like Sinosauropteryx and tyrannosauroids (Dilong), but barbed feathers [ie. actual feathers] are known only among the coelurosaur subgroup Maniraptora, which includes oviraptorosaurs, troodontids, dromaeosaurids, and birds. The description of feathered dinosaurs has not been without controversy; perhaps the most vocal critics have been Alan Feduccia and Theagarten Lingham-Soliar, who have proposed that protofeathers are the result of the decomposition of collagenous fiber that underlaid the dinosaurs' integument, and that maniraptoran dinosaurs with barbed feathers were not actually dinosaurs, but convergent with dinosaurs. However, their views have for the most part not been accepted by other researchers, to the point that the question of the scientific nature of Feduccia's proposals has been raised."