Copperhead maintains a fork called Noise available in their F-Droid repository

https://fdroid.copperhead.co/repo

The repo's signing key fingerprint (sha256) is

    F0 D4 EB 11 93 AD 82 FE B2 24 BD 11 74 B6 FB
    D8 9A 39 D8 ED 98 8C 9F FF 2A DD 0D CD 1C 4E
    27 1B

Kind of? https://zepman.tweakblogs.net/blog/12999/signal-on-android-w... (April 2016)