from selenium import webdriver as WebDriver
from selenium.webdriver.common.by import By

webdriver = WebDriver.Chrome()
webdriver.get("https://www.consorsbank.de/home")
shadowhost = webdriver.find_element(By.XPATH,"//wb-website-header")

# works
queryselector = "arguments[0].shadowRoot.querySelectorAll('div > button#header-login-button')"
elt1 = webdriver.execute_script(f"return {queryselector}", shadowhost)

# works not any more
queryselector = "arguments[0].querySelectorAll('div > button#header-login-button')"
shadowroot = webdriver.execute_script("return arguments[0].shadowRoot", shadowhost)
try:
    elt2a = webdriver.execute_script(f"return {queryselector}", shadowroot)
except:
    pass
shadowroot2 = shadowhost.shadow_root
try:
    elt2b = webdriver.execute_script(f"return {queryselector}", shadowroot2)
except:
    pass