[kovidgoyal]

Just to get you started, here is the login code:

    needs_subscription = 'optional'

    def get_browser(self):
        br = BasicNewsRecipe.get_browser(self)
        if self.username and self.password:
            br.open('http://m.lesechos.fr/abonnement/login.php')
            br.select_form(name="frmFusion")
            br['USER'] = self.username
            br['PASS'] = self.password
            br.submit()
        return br

I haven't tested it, it is based on inspecting the source code of the login page.

Then you need to write a parse_index() function to get the articles from the page you linked to. See https://manual.calibre-ebook.com/news.html