Depends on your budget.
Israel - highest quality but expensive.
Ukraine - good quality and fairly cheap.
India - decent quality and cheap.
* Obviously the above is a generalization - in each country in the world there are amazing and high quality people.

I have connections in all 3 of the above countries. Let me know if you need assistance with any projects.

I've successfully helped over 300 entrepreneurs, startups and businesses, and I would be happy to help you. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david

I did a massive research assignment for an innovation tech company on this last year.

If by quality you mean 1) able to speak english 2) diversity of code language 3) depth of code language 4) price in terms of salary 5) office cost in terms of real estate and location

Katowice, Poland
Riga, Latvia
Monterrey, Mexico

I have a contact for Katowice who often works with the government to setup offices for major companies. If you're serious and not going to waste my time on theirs, give me a call.

Ukraine is good once you'll find a perfect lead here. There are a lot of great developers and project managers here. Product management expertise is worse but growing for last 5 years.
But I found helping a startup to grow their team that the best solution is find a good lead, hr and grow the remote team starting from offline in Ukraine.