38c3, the 38th Chaos Communication Congress, is currently running.

https://events.ccc.de/congress/2024/infos/startpage.html

Yes, the root post is here: https://news.ycombinator.com/item?id=42537631

One of the greater hacker conferences in the year. (I am a huge fan of CCC and all events they do)

Each year, between Christmas and New Years. https://en.wikipedia.org/wiki/Chaos_Communication_Congress

Yes, the Chaos Computer Club in Germany. 27-30 Dec (So currently ongoing).

Yup, europe’s largest.