As I understood, your goal to get <div aria-labelledby='a'>text 2</div>
referenced to the <div id="a">text 1</div>
by id and aria-labelledby.
Solution is to find element by text 1 text, get id attribute and use it to search second div with aria-labelledby attribute:
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as ec
driver = webdriver.Chrome()
wait = WebDriverWait(driver, 10)
driver.get("some url")
id = wait.until(ec.visibility_of_element_located((By.XPATH, "//div[.='text 1']"))).get_attribute("id")
text2 = driver.find_element_by_css_selector(f"div[aria-labelledby='{id}']").text
# text2 = driver.find_element_by_xpath(f"//div[@aria-labelledby='{id}']").text
labelled_elements = driver.find_elements_by_xpath(f"//div[@aria-labelledby='{id}']")