I finally found a weird solution and I figured I should share it with the next one having the problem. I added the code to /mysite/_config/config.yml BUT I made a fresh install in another server. That worked! Interstingly enough, following the same steps in the first server didn't help. So I deleted the files of the server, copied and pasted the files from the second one (included .htaccess, which filezilla didn't recognize) and imported the database. Not elegant at all, but it worked!