Ask HN: Articles, references and best practices of DDoS defense

I am a software engineer that got interested in networking recently. I have now learned the basics of running a BGP setup (on providers like EquinixMetal) and would now like to learn the basics of DoS/DDoS defense, but I can't seem to find any articles whatsoever on the internet.

I am quite familiar with iptables/fail2ban management (to the level of locking down a machine and banning individual IPs / ranges etc.), but not so much in regard to efficient packet matching, detection and blocking etc.

Maybe I am googling wrong, but I just find promotional blog posts of companies offering DDoS protection or appliances, which is weird when you compare it to the countless things easily findable regarding software engineering of any kind. I'd really like to learn this stuff to feel more comfortable running my own BGP in the open on providers like the one mentioned above, but to me it seems like the information regarding this stuff is locked away from the general public and only available inside the brains of a few smart minds working at these companies. Just a feeling though, I hope to be wrong and that someone can point me to a few articles / guides where one who is new to this area can learn from them.