Are there any resources on deploying your own internal NNTP service
The standard software package is called INN ( https://www.eyrie.org/~eagle/software/inn/). It should come pre-packaged in upstream repositories for various linux distributions.
There's always newsgroups, which use NNTP (which isn't that dissimilar to email). They have existing groups in a hierarchy that can be subscribed to. It doesn't really give users the ability to create new newsgroups in the fly though.