[kovidgoyal]

Something like this (untested)

#!/usr/bin/env python
import threading
from io import BytesIO

from calibre.ebooks.BeautifulSoup import BeautifulSoup
from calibre.scraper.simple import read_url
from calibre.web.feeds.news import BasicNewsRecipe, classes


def absurl(url):
    if url.startswith('/'):
        url = 'https://www.science.org' + url
    return url



class Response(BytesIO):
    def __init__(self, url, text):
        super().__init__(text.encode('utf-8'))
        self.url = url
    def geturl(self): return self.url


class Browser:

    def __init__(self, local):
        self.thread_local = local
        self.thread_local.storage = []

    def open(self, url, *a, **kw):
        return Response(read_url(self.thread_local.storage, url), url)
    open_novisit = open


class science(BasicNewsRecipe):
    title = 'Science Journal'
    __author__ = 'unkn0wn'
    description = (
        'Science continues to publish the very best in research across the sciences, with articles that '
        'consistently rank among the most cited in the world.'
    )
    encoding = 'utf-8'
    no_javascript = True
    no_stylesheets = True
    remove_attributes = ['style', 'height', 'width']
    language = 'en'
    simultaneous_downloads = 1

    extra_css = '''
        .news-article__figure__caption {font-size:small; text-align:center;}
        .contributors, .core-self-citation, .meta-panel__left-content, .news-article__hero__top-meta,
		.news-article__hero__bottom-meta, #bibliography, #elettersSection {font-size:small;}
        img {display:block; margin:0 auto;}
        .core-lede {font-style:italic; color:#202020;}
    '''

    ignore_duplicate_articles = {'url'}

    keep_only_tags = [
        classes('meta-panel__left-content news-article__hero__info news-article__hero__figure bodySection'),
        dict(name='h1', attrs={'property':'name'}),
        classes('core-lede contributors core-self-citation'),
        dict(attrs={'data-core-wrapper':'content'})
    ]

    remove_tags = [
        classes('pb-ad')
    ]

    def __init__(self, *a, **kw):
        self.thread_local = threading.local()
        super().__init__(*a, **kw)

    def get_browser(self, *a, **kw):
        return Browser(self.thread_local)

    def preprocess_html(self, soup):
        for p in soup.findAll(attrs={'role':'paragraph'}):
            p.name = 'p'
        return soup

    def parse_index(self):
        url = 'https://www.science.org/toc/science/current'

        soup = BeautifulSoup(read_url([], url))
        tme = soup.find(**classes('journal-issue__vol'))
        if tme:
            self.timefmt = ' [%s]' % self.tag_to_string(tme).strip()
        det = soup.find(attrs={'id':'journal-issue-details'})
        if det:
            self.description = self.tag_to_string(det).strip()

        feeds = []

        div = soup.find('div', attrs={'class':'toc__body'})
        for sec in div.findAll('section', **classes('toc__section')):
            name = sec.find(**classes('sidebar-article-title--decorated'))
            section = self.tag_to_string(name).strip()
            self.log(section)

            articles = []

            for card in sec.findAll(**classes('card-header')):
                ti = card.find(**classes('article-title'))
                url = absurl(ti.a['href'])
                title = self.tag_to_string(ti).strip()
                desc = ''
                meta = card.find(**classes('card-meta'))
                if meta:
                    desc = self.tag_to_string(meta).strip()
                self.log('          ', title, '\n\t', desc, '\n\t', url)
                articles.append({'title': title, 'description':desc, 'url': url})
            feeds.append((section, articles))
        return feeds