A fair number of the questions to the martial arts StackExchange are about self defence. It makes some sense, often martial artists practise self protection skills and methods. However martial arts themselves only cover a small area of self protection, the recent question about devices for example is on topic for self protection but largely off topic for martial arts.
The skill and knowledge sets and training goals are also often not exactly aligned, though many martial artists may not realise it. It can mean poor advice and answers being given to questions which contain aspects of self defence questions.
There is also an information security stack exchange already, this specifically covers security aspects of using information systems, there are several additional SEs which cover different aspects of using information systems, and I don't think it's a bad model to follow.
I would certainly join such a SE, but probably wouldn't contribute many answers personally. I think it would be a valuable resource in particular if the community included people with amateur and professional experience.