Most Spanish developers will write a README.md file in Spanish explaining the list. Look for keywords:
You cannot play an M3U file with just any music player. You need software capable of handling streaming protocols. Here are the best options: listas m3u espana github
If you are a tech-savvy user who wants to watch Antena 3 or Cuatro on your laptop for free, and you don't mind occasional buffering, then hunting for is a fun hobby. Most Spanish developers will write a README