what do you even mean?! start what at the kernel?

kernel is locked and most phones can't be rooted anymore

Just recalling from memory, Linus Torvalds wasn't making a free and open source kernel at first. He was making a kernel yes, but he attended a Richard Stallman speech where Stallman introduced GNU and expressed that he needed a kernel cause AT&T was cracking down on Unix clones. And Linus was moved by that enough to change gears and renamed the project to Linus Unix aka Linux. Anyone who remembers better or has sources, correct me below, I'm writing from memory. My point is though that Linus wasn't originally intending to make a free and open source kernel.