I believe that the solution that I end up choosing will depend on the optimal results of the user.
Adding a home page selector can be a solution to present all the calculators without having to use the menus, but you probably want to see how users work with the calculators in your application. Suppose you open the application to perform a quick calculation several times, and each time you have to relocate the correct calculator and then enter the values, this additional step is added after a while and makes the experience less rewarding.
In addition, if users perform multiple calculations during a session, then the solution of the home page would mean that they should return, select the calculator, perform the operation and return to select the next one, this will also add up and increase the friction.
In short, users do not seek to use the calculator, or even produce the resulting calculation, instead they are configuring and improving their rowing objectives, so the focus must be on the most effective way to return to their activity.
Consider swiping and other gestures that allow users to move between different views. Not only is it preferred for situations where users are busy with other things, but it is easy to memorize where things are after repeated use. This will also make it easier for them to discover their premium calculators.