TLDR, I voted “I didn’t start with D&D,” but it’s kind of complicated what constitutes “starting” and also what constitutes “D&D.” D&D kind of defined my gaming experience for many years, despite not always being the rules system I used.
As the annoying-yonger-sibling’s-best-friend to a regular D&D group in the 90s, I grew up having D&D deeply intertwined with my developing interest in fantasy, and I spent many years incorporating concepts I had passively absorbed from D&D into my childhood roleplaying. And not just “lore” elements like pretending to be elves or borrowing proper nouns from D&D settings, but actual pseudo game mechanics my friends and I would make up and play by. At a couple of points in probably 5th-7th grade I tried to essentially DM a game with maps drawn on graph paper and pretty much entirely improvised dice mechanics for some friends, just based on my outsider’s impression of what roleplaying games looked like.
It wasn’t until 8th grade that I switched schools and met someone who was both familiar with actual published RPGs and willing to teach me to play them. At that time we played several different systems in rapid succession, and I don’t remember what specific systems we tried or which was first, but I remember that among them were D&D, and some d6-based system that to me came across as functionally D&D without as many cool different dice. We also tried Call of Cthulhu but my understanding of probability was not yet good enough to produce a competent character in a percentile system and I hated it, so we switched to the d20 conversion (I actually still have the book for that!)