How to display the publication date on articles?

Link to your page please?

Is your Front Page pointing at a Page or Posts?

https://isentinel.eu/

Yes my front page points at posts.

Have you suppressed ‘entry-meta’ with your CSS? (I can’t see it, but if that wasn’t suppressed, you’d be getting the usual post details)

See my test site: https://www.rdell.co.uk/news/

Well I created a child theme with a whole new CSS, so perhaps is it that reason.

What do you think I should write in the CSS thus ?

Check your Settings>Reading. Do you have Full Text or Summary selected?

Full text !