You need one schedule C for each "business". If you have more than one business, and you use the same vehicle for each business, you keep track of the mileage separately and you enter the vehicle mileage separately for each business.
If you entered separate 1099s for Lyft, Doordash and Uber, it sounds like Turbotax might have created 3 different schedule C businesses.
However, you are allowed to combine related business activities under one schedule C. Since this is all basically ride share, and the type of work and type of expenses are very similar, you could combine all your 1099s under one business and one schedule C called "ride share". Then you would enter all your rideshare income, car expenses, and other expenses, on one schedule C
If you want to combine the businesses, you will need to delete all 3 schedule Cs and then create one business for rideshare with all your income and expenses. If you really are using the Live Online version, your Live expert can help you with this.
