There is https://www.eternal-september.org. For me the biggest hurdle tbh was finding an email provider that was 1) anonymous (including not requiring my credit card obvi) so that I could have a specific identity for Usenet 2) had IMAP/POP3 support so I could use it with Thunderbird and 3) wasn't gmail, yahoo or outlook/hotmail because I already have accounts with those and don't want to keep switching. I actually failed, I ended up having to pay the email provider I'd picked for IMAP support.