How to download free app without Apple ID

My country (Serbia) is not listed as one of the countries, so I understand that I can't purchases any app, but what happens with free apps like viber for example ?

I cannot finish my my apple IP registration until I choose country even if I don't want to register credit card. I choose payment method none and still can't finish registration without selecting the country.

Please advise how to download viber.

Thank you.