What are the Hungarian and Russian idioms?
Note that "idiom" in English has two separate meanings, and one of them (1) defines the same concept as the Polish definition does. The other one (2) means something different - a particular way of expression typical of a group or an individual. None of the two English definitions , in my opinion, cover the expression "out of the beaten track".Idiom a frazeologizm - Poradnia językowa PWN
one could even argue that even English 'off the beaten track' is not an idiom, since you can infer the meaning of the expression from its parts.
On the other hand, using the definition from:
IDIOM | meaning in the Cambridge English Dictionary
you'd have to classify both as idioms.