Where do you learn about new and existing TTP's?

For the most part, I've found SANS content to be great. That and another post on this subreddit about SANS got me thinking. Where else do you go (other than here) to learn more about adversarial attacks or blackhat techniques in great detail?

I often see SANS looked at as one of the greatest resources but I can't help but feel like they gatekeep info via cost. Where else do you turn to?

adversarial adversarial attacks attacks blackhat cybersecurity found great learn sans techniques thinking ttp