How useful is a Corporate Strategy internship with getting into MBB?

1. That'd be a great internship to get as a sophomore (or even as a junior it'd be good if consulting internship recruitment strikes out)
2. Many F500s do not allow sophomore (i.e. rising junior summer) interns, but many also do. It's up to you to figure out which companies recruit sophomores through working with your career center, asking others in clubs you're in, looking at company websites, and referencing LinkedIn. You do not want to be in a position where you don't have a good internship until rising senior year, since that'll hinder your ability to get a good consulting internship

I also want to add -- many F500s don't have interns on strategy teams, you can imagine more uncommon would be sophomore strategy interns. If you find such opportunities great, but if not getting a F500 finance or other internship in your field of study would be more plausible