The best alternative is LinkedIn that you use with some restraint instead of connecting to thousands of people and opening up your profile and email to absolute

The best alternative is LinkedIn that you use with some restraint instead of connecting to thousands of people and opening up your profile and email to absolutely everyone. Outside of that you probably won't find many alternatives because the large social network is the whole point - the value proposition of LinkedIn is that it's the one place where everyone goes to search for jobs and employees. A less well-known platform can't give you the same benefits by definition.