https://www.techradar.com/news/best-free-usenet-trial

Free Usenet servers have seen their numbers dwindle as demand for (and the sheer cost of) resources has continued to increase. They have become less reliable, more unstable, and far slower than paid options.

On top of that, they tend to have short binary retention periods (only a few months) and they do not usually provide an SSL certificate to improve security and maintain anonymity.