I've had this conversation a few times in the week or so. Usenet still exists, but to what extent I have no idea. It might be worth to try out Giganews or any number of other providers.

A few newsgroups are still reasonably active. I still frequent comp.lang.lisp and comp.lang.ada. Though they now have tons of spam in them so the interesting parts are somewhere in the garbage. I think most groups have moved to other discussion boards/systems as their primary forum now, and newer groups don't try to create a newsgroup. For instance, I doubt there's a comp.lang.elixir or comp.lang.rust.

As a discussion system, it's pretty much defunct at this point.

You don't see very much spam arriving at the Eternal September or AIOE news servers.

It's pretty much fine as a discussion forum.

Things have been lively in comp.lang.c recently with a little coding exercise going on and such.

comp.unix.programmer and comp.unix.shell are active also.

comp.theory has been quite active due to a crackpot who insists that he has solved the halting problem, or at least refuted common halting proofs using a nested x86 simulator that detects recursion, haha.