Get Youtube video storyboard using ID/URL

You can utilize Youtube iFrame Player API where storyboard url available (not documented) in player object right after player initialization and start playing OR just using player.seekTo(0). Look for playerInfo.storyboardFormat:

<script>
    function onPlayerStateChange(event) {
        if (event.target.playerInfo.storyboardFormat) {
            story_board_data = decodeURIComponent(event.target.playerInfo.storyboardFormat).split('|').map(function(el, n){
                return !n ? el : el.split('#');
            });
            event.target.destroy();
            document.getElementById('storyboard').src = story_board_data[0].replace('L$L/$N','L2/M0')+'&sigh='+story_board_data[3][7];
        }
    }
    function onPlayerReady(event) {
      event.target.mute();
      event.target.seekTo(0);
    }

    function onYouTubeIframeAPIReady() {
      var player = new YT.Player('player', {
          width: 1, height: 1,
          videoId: '7nN5g0bu7v4',
          events: {
              onReady: onPlayerReady,
              onStateChange: onPlayerStateChange,
          }
      });
    }
</script>

<div id="player"></div>
<img id="storyboard">
<script src="https://www.youtube.com/iframe_api"></script>

JSFiddle snippet works fine with iFrames, check it in action.

I managed to do this in Python with Playwright, and a seperate JavaScript file that playwright can just read in and then run:

main.py

import os
from playwright.sync_api import sync_playwright

def get_storyboard_urls(video_id):
    # Load javascript
    script_path = os.path.join(os.path.dirname(__file__), 'storyboard_extractor.js')
    with open(script_path, 'r') as f:
        js_code = f.read()

    # Run playwright
    with sync_playwright() as p:
        browser = p.chromium.launch(headless=True)
        page = browser.new_page()
        try:
            page.goto(f"https://www.youtube.com/watch?v={video_id}")            
            storyboard_urls = page.evaluate(js_code)
            if storyboard_urls is None or storyboard_urls == "":
                raise ValueError(f"Failed to fetch storyboard URL for {video_id}\nValue returned: {storyboard_urls}")
            return storyboard_urls
        except Exception as e:
            print(f"Error fetching storyboard URL: {e}")
            raise e
        finally:
            browser.close()

get_storyboard_urls("nr0RPVvKWDI")

storyboard_extractor.js - a bit more detail in this answer

// This script extracts the storyboard URLs from a YouTube video page
() => {
    // Storyboard Get
    const resp = ytplayer.config.args.raw_player_response;
    const storyboards = resp.storyboards;
    const specRend = storyboards.playerStoryboardSpecRenderer;
    const spec = specRend.spec;

    const parts = spec.split("|")
    const base_n = (n) => parts[0].replace('L$L/$N',`L${n}/M0`);

    const signs = parts.map(p => p.split("rs$")[1]).filter(p => !!p).map(p => "rs%24" + p);

    // Output
    urls = []
    for (let i = 0; i < signs.length; i++) {
        let url = `${base_n(i)}&sigh=${signs[i]}`
        urls.push(url)
    }
    return urls
}