Destinations in Poland such as Krakow are definitely becoming city break destinations (as per Jet2 from LBA)
Becoming? Krakow (and Budapest, Prague) have been city break destinations for best part of a quarter of a century. Even the likes of Gdansk following in their trail have been recognised some time! When I flew to/from Krakow shortly after EU entry probably 80% or more of pax were British. I have admittedly also seen other flights board (eg Szczecin) where I don’t think a single person was British.