I don't know how this is a "shortcut"...... You have to have a starter.... with or without a scoby. The scoby does not make kombucha, the microbes that are on it and in the starter do.
This is equivalent of making bread or beer using wild yeasts..... It's possible in theory, but the very specific species of acetobacter and yeast that make kombucha as we know it have evolved over time with kombucha being passed from hand to hand throughout the centuries. To do it yourself from scratch might take generations. I don't know how many hundreds of years you are willing to dedicate to the task............
Set some sweet tea outdoors covered with a cheese cloth to keep the insects out. It likely will gather some wild yeast if it's in a suitable location in summer. It will ferment and produce alcohol, and that will sour naturally from naturally occurring acetobacter if left in the open. This would be the starting point. If the result is not what you want, try doing the same thing in Mongolia, or Spain, or Eastern Europe......... Keep trying again and again, and eventually you might get a result you like.
Remember that the SCOBY is misnamed It is not a symbiotic colony of yeast and bacteria. It's simply a pellicle created of microcellulose by acetobacter. This pellicle can be seen in nature anyplace acetobacter is souring anything. The symbiosis is a bit of a myth. The yeast produces alcohol, and the acetobacter sours it. This offers no benefit to the yeast, and actually stops fermentation when the acidity reaches an intolerable level. If this is "symbiosis", then we must regard a lot of things as symbiosis that are not.......... Such as shooting a deer to eat..... Is the relationship between a hunter and a deer "symbiotic"? Perhaps if the hunter creates an environment that is beneficial to deer in general..... which could be said to be true, as deer thrive in hay fields. We must then regard all relationships in nature as symbiotic. Cancer for example. The host creates the environment for cancer to grow in........ Is this symbiotic?
H.W.