Me gustaría sincronizar automáticamente las entradas de WP con los temas existentes de Discourse si tienen el mismo nombre. ¿Cómo obtener un tema por título?

You could do it manually with this:

Or write a script that calls a function similar to this:

Since you only have the topic titles, and not the topic ids, I think you’ll need to make a request to the Discourse topic without the id and get the redirect that’s returned from Discourse. Something like curl http://localhost:3000/t/your-topic-without-the-id -s -L -I -o /dev/null -w '%{url_effective}'