Websites like Commaful and Storybird are specifically designed for posting short stories. They offer user-friendly interfaces and communities of fellow writers who can provide feedback and support.
Well, you might look into platforms such as Archive of Our Own (AO3), which is great for various types of stories. Or, if you prefer a more professional setup, try pitching to literary magazines' online editions. Some well-known ones include The New Yorker and The Atlantic. Just make sure to read their submission guidelines first!