Usenet is a worldwide distributed electronic bulletin board system
smfr.org
smfr.org
Also people posting from Google Groups no longer sends their posts to USENET. That means spam has dropped quite a bit.
There are a few free providers you can use to access USENET, a simple search should bring them up.
The last time I tried (probably about a decade at this point) it was pretty much entirely spam.
But if Google Groups doesn't send out to USENET, is it just its own closed system like Yahoo Groups used to be or something?
I do not know as I never used it after they killed the old dejanews interface. But Google did cut it off from USENET sometime last year.