Are they not? My cartridge of Mario Kart 8 is Japanese, the one of Just Dance 2018 is an US version and all my other game cartridges are European (3 international, 1 UK, 1 French and 2 German versions), so technically there shouldn't be a problem unless they changed something
the console is region free. I have Korean, Asian, Japanese, and US and EU games. Only continental Chinese games have a lock, I suppose.