Another useful source is the archives that exist for the old bitcoin-* IRC logs. A lot of discussion was there back in the day.
There’s gnusha.org and there’s a few others, but with a caveat:
Here’s Poelstra’s archive of *-wizards:
this is AJ Towns’ for #bitcoin-core-dev going back to 2015:
The caveat is, I don’t think any of these really go back much beyond 2014-15. However, this one is Kanzure’s archive tarball (for #bitcoin-dev, #bitcoin-core-dev (which is later anyway) and #bitcoin-otc (for some reason) specifically):
https://diyhpl.us/~bryan/irc/bitcoin/bitcoin-logs.2010-2018.tar.bz2
… which does go back to 2010. It might be the only source for that (?).
It would indeed be nice to have something you could query which knew every one of the historical conversations on technical topics. Not easy, but clearly LLM tech can partially help.