I would go to medium.com and in the magnifying glass search box type a subject that interests you, say philosophy; then hit return.

Under "Results for Philosophy" click the "Publications" heading. That'll list a bunch of publications on that subject.

Most publications has a tab like "writer for us" and many also show how many followers they have.

The key is to find publications that you like, that contains articles like yours, and then follow the instructions to write for them.

I hope this helps.