I'm not sure about legal places to read it for free. It's best to support the creators by using authorized platforms that might require a subscription or purchase.
You can start by looking on fanfic websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, including Jinx manhwa. Another place could be FanFiction.net. There are often dedicated sections for different manhwa, and you might be able to find some great Jinx - related fanfics there. Additionally, some manhwa - specific forums or communities might also have users sharing their own Jinx fanfics or recommending good ones.
You might find Jinx manga on dedicated manga apps like Comixology or Shonen Jump. Another option is to search on bookstore websites that sell digital comics. Just make sure you're accessing legal and authorized sources for the best reading experience.