How do I search for internships off-campus?

Brief intro about myself- I am a male 3rd year undergrad at IITD, not from a circuital department. Companies such as Amazon, Google, Flipkart and Adobe have already hired students from campus but they filter students via branch i.e. unless you're in CS, Maths or Electrical it's close to impossible to land an internship in SDE. Most top students in CS go for HFT companies but still recruiters prefer low GPA CS students over somebody from say mechanical or chemical. I've solved around 200 problems on leetcode/CF and I want to apply to companies by myself off-campus from January. How should I go about it and what are things I should be doing along with my college academics to increase my chances of landing an internship?!