Recently founded. Only 6 countries
Sure, I didn't say it's popular, just that it exists.
But tbh hockey is also quite popular in countries like Germany (is clearly behind handball though), Austria and Switzerland. And we shouldn't forget Russia with their big population. Yeah, I know many Russian clubs competing in the KHL (which is the 2nd best hockey league in the world) are located in Asia but most people still live in European Russia.
OTOH volleyball is very popular in Italy (their league is the best in the world), again in Russia, Poland, Turkey,... which are all countries with big population.
So I'm not sure handball should so clearly be considered as a no. 3 behind football and basketball.