Tips for Landing a YC Internship?

I'm a rising sophmore in university, and I really want to work for a YC-backed startup this Fall (leaning towards consumer products). I think I have solid experience (interned at AWS this summer as a SWE, and I've also built and scaled consumer mobile apps solo to 20k+ downloads). My main method so fair has been sending cold DMs to founders on Linkedin for startups I find interesting, but so far I've had no luck. Any advice?