I wouldn't really classify it as a "good" nntp server (nor would I recommend it as it's probably not fully compliant) but nntpchan is one possible route if you don't mind the imageboard aftertaste. it's not meant for mainline usenet. I made it out of frustration with INN's feed syntax and because another daemon that I used at the time was abandoned written in python (it was an abomination but it worked).

https://github.com/majestrate/nntpchan

Depending on your usecase, Leafnode might be reasonable.

Personally, when I needed NNTP I sprung straight for INN, but be prepared to educate yourself.

http://leafnode.sourceforge.net/ https://www.eyrie.org/~eagle/software/inn/