My own experience was that getting into software development took up about half of my free time from around age 12 to 18 and after some fumbling around some friends and I were at an intermediate hobbyist level before graduating high school (probably at or just barely beyond the level of the best bootcamp students). We even ran a couple of clubs. I didn't do an internship, but just found part time work building simple CRUD apps for a few local small businesses (low stakes contracts of a few thousand bucks were awarded thanks to a friend who was playing with daddy's money while finishing his business degree). Then I got my first "real job" (salaried, benefits, etc.) a few months after finishing an accredited bachelor's degree in CS at my state school. The rest has been my actual career until now (I finished college about a decade ago).
I'm pretty sure this is the only "reliable" way and it wasn't easy. I had a couple of mental/ego breakdowns along the way because I found out I'm just kinda smart and not a genius, I didn't grow up to be a millionaire game designer like Carmack or Romero, and I became somewhat out of shape. I think this is... such a painfully average life story?