Shortening the Let's Encrypt Chain of Trust https://letsencrypt.org/2023/07/10/cross-sign-expiration.html
"If you use Android 7.0 or earlier, you may need to take action to ensure you can still access websites secured by Let’s Encrypt certificates."
旧端末セーフ。Firefox入ってるけど、設定弄ってて認証まわりChromeじゃないと危ういからよかった