The gateway between Google Groups and certain newsgroups is still running, in both directions. For example, I received a copy of this Groups posting https://groups.google.com/g/de.soc.recht.steuern+buchfuehrun... over regular Usenet NNTP.

The technology is still up and running. Some of the people from the 90s are still there. But Usenet definitely has peaked in terms of users and postings.