Does anybody know how to identify shadow dom web elements using selenium webdriver?

You can inject this piece of javascript that does this and then run the find_element methods on that element:

shadow_section = mydriver.execute_script('''return document.querySelector("neon-animatable").shadowRoot''')
shadow_section.find_element_by_css(".flex")

since you use often that you may create a function, , then the above becomes:

def select_shadow_element_by_css_selector(selector):
  running_script = 'return document.querySelector("%s").shadowRoot' % selector
  element = driver.execute_script(running_script)
  return element

shadow_section = select_shadow_element_by_css_selector("neon-animatable")
shadow_section.find_element_by_css(".flex")

on the resulting element you can put any of the methods:

find_element_by_id
find_element_by_name
find_element_by_xpath
find_element_by_link_text
find_element_by_partial_link_text
find_element_by_tag_name
find_element_by_class_name
find_element_by_css_selector

To find multiple elements (these methods will return a list):

find_elements_by_name
find_elements_by_xpath
find_elements_by_link_text
find_elements_by_partial_link_text
find_elements_by_tag_name
find_elements_by_class_name
find_elements_by_css_selector

later edit:

many times the root elements are nested and the second nested element is no longer available in document, but is available in the current accessed shadow root. I think is better to use the selenium selectors and inject the script just to take the shadow root:

def expand_shadow_element(element):
  shadow_root = driver.execute_script('return arguments[0].shadowRoot', element)
  return shadow_root

#the above becomes 
shadow_section = expand_shadow_element(find_element_by_tag_name("neon-animatable"))
shadow_section.find_element_by_css(".flex")

To put this into perspective I just added a testable example with Chrome's download page, clicking the search button needs open 3 nested shadow root elements:

import selenium
from selenium import webdriver
driver = webdriver.Chrome()


def expand_shadow_element(element):
  shadow_root = driver.execute_script('return arguments[0].shadowRoot', element)
  return shadow_root

selenium.__file__
driver.get("chrome://downloads")
root1 = driver.find_element_by_tag_name('downloads-manager')
shadow_root1 = expand_shadow_element(root1)

root2 = shadow_root1.find_element_by_css_selector('downloads-toolbar')
shadow_root2 = expand_shadow_element(root2)

root3 = shadow_root2.find_element_by_css_selector('cr-search-field')
shadow_root3 = expand_shadow_element(root3)

search_button = shadow_root3.find_element_by_css_selector("#search-button")
search_button.click()