a hook for wordpress article introduction

Hi there,

you can hook in before it using: generate_after_entry_header hook.
See here:

https://docs.generatepress.com/article/hooks-visual-guide/#posts-page

Or are you want to do something with the Excerpt ?

Good morning,

sorry, I'm having trouble expressing myself, I'm looking for the hook that I'm going to put in the dynamic content of generatepress

Ok, so are you wanting to display the "Extrait" in a Block Element ?
If so, add a GP Dynamic Content Block:

https://docs.generatepress.com/article/dynamic-blocks/#dynamic-content

and select the Post Excerpt