CertPathValidatorException connecting to a Let's Encrypt host on Android M or earlier

Question

[edit: If you are here for Let\'s Encrypt expiry event from January 2021, read this first https://letsencrypt.org/2020/12/21/extending-android-compatibility.html]

Answer 1

On Android Nougat (7) you can add/update android:networkSecurityConfig in AndroidManifest.xml to point to a local certificate.

https://www.danieldent.com/blog/android-apps-lets-encrypt-dst-root-expiry/