Article in Polish has some details and a flight map: https://www.onet.pl/turystyka/onetpodroze/samolot-pasazerski...

Interestingly, the Enter Air spokesperson said:

"The plane was passing over a thunderstorm, and Slovak flight controls directed it to this route. It all went according to safety procedures."

It's hard to understand what safety procedures they meant.

Probably the “do not enter a thunderstorm at all costs, even if you have to enter a war zone.”