Are there really still any big "well-kept secrets" left on this topic?
I feel like if you've travelled around, talked to people, and even read online you probably have a decent general idea on what places are like/will be like. There are definitely to be said about logistics, cold approach volume, and live-ability of course, but after living and doing pickup across several continents and countries, I've became a little skeptical on the idea of "hidden gems" with regards to easiness, quality of women, results, etc. People have tried all the big cities and know what's there. And while you can still find a lot of success in smaller places, it can get difficult getting volume in.
For example will your results really be that different in Zagreb vs Belgrade? (I don't know, I've only done pickup in one EE city before, but I'd guess not really). If you do think there are some real hidden gems left - feel free to dm me, I'd love to discuss this (I was really fixated on the question a couple years ago, so I have some opinions on that subject). There are some lesser-discussed regions of the world that I am still really curious about checking out someday.
I'm not really convinced that talking about destinations on a forum like this will really make a difference in any location discussed here. I'm not convinced that there are that many locations where men travelling for dating have meaningfully degraded the dating scene either (though there definitely are a handful)