Outlook killed NNTP 20 years ago by virtue of not supporting it (every other mail client at the time did).
it also suffered as a discussion medium because of the decentralized unauthenticated measure, for sure - I don’t think the global hierarchy would have done much better than it did.
But two companies I was consulting for around 2000 had very effective NNTP internal servers, and both switched them off around the same time because Outlook didn’t support them (Outlook Express did, but that’s not helpful)
One just went the “reply all” route. One used a mailing list (majordomo, iirc). Neither worked remotely as well as NNTP did.
NNTP does support authentication (with username/password or with SASL), although I don't know which client programs implement it (my own currently doesn't, although this could be fixed in future).
You could use a mailing list and/or web forum with the same messages as the NNTP. I have my own NNTP server software with partial implementation of a web forum but none of a mailing list yet; I would hope to fix this. Other software might already do this, I don't know. (I know there are programs that can duplicate the messages and make them available, but I don't know if there are those that will use the same message database for all three and/or that will use NNTP as the "main format".)
Synchronet might be able to do it; I know it has many functions, including Telnet, NNTP, email, IRC, FidoNet, HTTP(S), SSH, Gopher, PETSCII, etc. There is a web forum too. (As far as I know, it doesn't have Gemini yet.) However, Synchronet is a complicated software, and is designed for a BBS and might not be what you wanted, so having other software can be good if a BBS is not the kind of service you intended to run, I think.
The authentication/federation problem is what killed the public nntp use even among the non-Outlook users; But it was Outlook that had killed it among corporate and professional users. Those are two independent issues.
Gmane[0][1] did bidirectional nntp to mailing-list in 2002; But there's a mismatch, both technical and cultural, with these gateways.
Also, in an internal system, the IT department has to be willing to support them, and they weren't in my cases.
It's now water under the bridge. NNTP is essentially dead except for legally questionable video distribution.
it also suffered as a discussion medium because of the decentralized unauthenticated measure, for sure - I don’t think the global hierarchy would have done much better than it did.
But two companies I was consulting for around 2000 had very effective NNTP internal servers, and both switched them off around the same time because Outlook didn’t support them (Outlook Express did, but that’s not helpful)
One just went the “reply all” route. One used a mailing list (majordomo, iirc). Neither worked remotely as well as NNTP did.