Yes many platforms do provide free courses for JEE mains the following are the  instructions you can refer or go through for accessing:

1.Unacademy Free Live Classes:
They provide daily live and recorded sessions for Physics, Chemistry, and Maths
You can learn from top educators and access previous year question papers also.

2.Careers360 free crash course:

They offer a 100+ hours of live classes, quizzes, and mock tests which also covers all key topics with expert mentors.

3. You can refer YouTube Channels with Free JEE Content:

Physics Wallah : A Well-Known  channel for high-quality lectures in Physics, Chemistry, and Maths.
Mohit Tyagi : If you want to dive into advance Math then it is great for advanced Maths concepts.
Unacademy JEE : Live and recorded classes from top educators
Just search these names on YouTube and dive into their playlists.