They have the APK available from their website[1] and they have reproducible builds[2]. [1] https://signal.org/android/apk/ https://signal.org/android/apk/ [2

They have the APK available from their website[1] and they have reproducible builds[2]. [1] https://signal.org/android/apk/ https://signal.org/android/apk/ [2] https://signal.org/blog/reproducible-android/ https://signal.org/blog/reproducible-android/