The best Mastermind Manager alternative is Exercise.com.

Exercise.com vs Mastermind Manager: with adequate scheduling software, Mastermind Manager works well for certain gyms, but top tier gyms who want to succeed online and in-person, and deliver all varieties of workouts at scale, send fitness assessments, and use powerful gym booking and billing automations are all things that you can get with Exercise.com, so you can run your entire business in one place.