I agree. And, I also wrote a NNTP server software (and I run it on my computer), which is smaller than the other ones (it is a single source file with less than

I agree. And, I also wrote a NNTP server software (and I run it on my computer), which is smaller than the other ones (it is a single source file with less than 2600 lines of code), and uses a SQLite database to store the data. (You could also provide other interfaces to the same data, such as a mailing list and a web interface, although my software does not currently have these features.) (I don't use Slack myself, and I do not intend to. For my own projects I can use IRC and NNTP.)