Universities (at least certain ones) and startups (more in absolute terms than universities, but there's also a much bigger fraction of swindlers). Most blogs and forums are garbage. If you're not inside these ecosystems, try to find out who the smart/talented people are by reading influential papers. Then you can start following them on X, linkedin etc. and often you'll see what they're up to next. For example, there's a pretty clear research paper and hiring trail of certain people that eventually led to GPT-4, even though OpenAI never published anything on the architecture.