This is the 3325th most frequent Polish word.
ukraińskimi
"Ukraińskimi" means "Ukrainian" in the instrumental plural form in English.
In this sentence, 'ukraińskimi' is an instrumental plural form of the adjective 'ukraiński', describing the nationality or origin of the authors discussed by the teacher.
Nauczyciel omawiał zagadnienia związane z ukraińskimi autorami literatury.
The teacher discussed topics related to Ukrainian literature authors.
Here, 'ukraińskimi' modifies 'malarzami', and similarly indicates the noun's association with something Ukrainian, as part of the conversation following the exhibition.
Zainteresowałem się ukraińskimi malarzami po obejrzeniu wystawy w muzeum.
I became interested in Ukrainian painters after seeing the exhibition at the museum.
In this usage, 'ukraińskimi' modifies 'zespołami', linking the musical bands to the Ukrainian context.