Strainge Beast hard kombucha is built upon 2 core teas
Organic Green Tea
Organic Black Tea
While the vagueness of the origin and specific types of green and black teas used may seem discouraging at first, having a detailed answer may not be that important.
The distinctive flavor profile found in tea leaves is can be minimized or lost by the work of the SCOBY, especially when additional ingredients/flavor are added. Other than color and (possibly) the ability of the SCOBY to process the tea, specific tea ingredients can make a less noticeable impact on the final beverage experience. A combination of basic organic greens and black teas constitute the base for may kombuchas, as it is believed to provide a fairly neutral colored liquid (not too light/dark) and provide a balanced environment for the SCOBY to do its work.
The process then comes down to selecting the cut size of the tea leaves that meet any requirements for filtration and speed/intensity of brewing/steeping. For example, smaller leaf cuts steep faster than larger, whole leaves.