The Internet is a distributed system. Usenet was never centrally hosted anywhere AFAIK. It was scattered around lots of individual systems. You'd have to look up the detailed history but Deja News brought together what it could at one point. It was subsequently purchased by Google and it was folded into Google Groups.

Back in the old days (mid 90's and earlier), most universities and large corporations had their own Usenet servers. These peered with other servers, either over the Internet with NNTP, or through older protocols like UUCP using modems.

I had a UUCP news feed from a local internet provider when I was in high school, back in 1993 or so.