MethRaptor Did you install Google Play services before Signal, or did you first install Signal and then Google Play services? I ask because if you install Play services first and then Signal, even if you remove Play services later, Signal is still dependent on it.
On the other hand, if you install Signal first, it will set up its own background process. While I haven't tested it personally, I believe Signal's own background process will only work on active profiles and may stop if you switch user profiles.