For the first time in ages, I actually had a quick skim through the list of all the boards on MN: www.mumsnet.com/Talk
Virtually everywhere I went someone had made a recent post (June 2021), often to my surprise, eg the completely non-descript Other subjects or the less topical Wimbledon, World Cup, Skiing and Christmas. 
There's even a board called Ethical dilemmas which appears to tick along ignoring its noisy neighbours in AIBU. 
The most inactive thread I could find was Refugee crisis which apart from one poster realising they were responding to a zombie thread hasn't had an on-topic post since 2019!
So can you find one that's even more obscure? surprising? Do you know a board with less traffic that you'd love to see get more attention?
Bonus question: what board should exist that doesn't?