For me, it was gradual. I used windows and tbe same proprietary software as everyone else, but then I stumbled upon the concept of open source. I was a kid, and this felt like something amazing, so I started downloading all foss software I could. I was amazed by how lightweight everything was. My pc was old, my internet was slow, and and my storage space was low, but foss software made my machine feel much better. When I discovered Linux (before that, I didn’t know the OS was a software like all others, and that it could be replaced too), I was already using everything foss, and the transition was so smooth.