What are your favourite newsgroups?

On the back of today's earlier discussion on the possibility of a Usenet revival/replacing Reddit (https://news.ycombinator.com/item?id=36153565), I went and created an account on Eternal September.

I've lurked on Usenet a bit before and came to the conclusion that while there's a lot of spam, there are still a few active/well-moderated newsgroups worth joining.

To that end, which high-quality newsgroups do people recommend?