Very sorry, but I've now decided I need to block access to https://newsgrouper.org.uk/ from the UK, starting 16th March. This is because I find it impractical to meet the requirements of the UK's Online Safety Act, which comes into effect then. See https://www.ofcom.org.uk/online-safety and https://onlinesafetyact.co.uk/
I've done a fair bit more homework on this, reading some of the guidance, but not all the thousands of pages that Ofcom has produced, and following their online seminars. Unfortunately very many aspects remain vague, and requests to Ofcom to provide clearer guidelines get answers like "It depends on your circumstances", "We can't advise individual sites", "You have to make the judgement", etc..
I'm afraid my conclusion is that trying to comply with the OSA is just too much effort. It's not just the initial risk assessments and policy/system changes. It's also that one is then required to respond to any reports that come in and judge whether that content is really illegal. You are required to remove anything that is illegal under a long list of categories, but also to protect users' right to freedom of speech. It's easy to think of cases where this balance could be very tricky. I simply don't want to get into the business of having to police other people's speech.
Ofcom have stated unequivocally that geo-blocking the UK will put a site outside the scope of the Act. So I put up a simple survey on the newsgrouper site, this appeared for UK users only, and I let it run for two weeks. There was just one question and a space for comments. I got 11 responses, as follows:
How would a UK block affect you? Answers
1: Not Concerned, I can follow Usenet by other means. 1
2: An Annoyance, but not the end of the world. 5
3: Oh No, that would be a disaster! 5
The comments were generally disappointed, but some also expressed understanding. So blocking UK access would be a real inconvenience to 5 people. I regret that, but they may be able to use one of the other web interfaces to Usenet, see: https://en.wikipedia.org/wiki/Web-based_Usenet#Web-based_sites_and_popularity . Also UK people are only about 15% of my users now.
I have seen comments that having a .uk address is enough to bring a site into the scope of the act. I'm not convinced about that, but to be on the safe side I have reregistered my site as newsgrouper.org with a redirect from newsgrouper.org.uk .
My software is available at: https://chiselapp.com/user/cmacleod/repository/newsgrouper/home so if anyone else wants to take on the job of running an instance that would remain open to UK users, they are welcome to do so.
It gives you many options on what to use, you can use Llama which is offline. Needs to be enabled though about:config > browser.ml.chat.hideLocalhost.