I haven't tried it for replacing TLS certificates, but you do not need a rooted phone to mess with 3rd party apps on android. You can unpack an APK and re-sign

I haven't tried it for replacing TLS certificates, but you do not need a rooted phone to mess with 3rd party apps on android. You can unpack an APK and re-sign it using your own key, allowing you to make whatever modifications to the APK you want. In addition to making whatever changes you want to directly (such as just replacing the pinned certificates), you can update the manifest to set the android:debuggable flag to true, which allows you to access and modify the apps private files through ADB. The main downside of this approach is you cannot do an in-place replacement of already installed app, as your version is signed by a different key. You need to uninstall the previous version first, causing you to lose existing app data. At one point, I was able to work around this using Android's backup feature, but I never bothered to retain data since then since it was too much of a hassle and turned out not to matter that much for any of the apps I was playing with.