You can use Signal with MicroG[0] and "checkin" to GCM in order for notifications for queue wakeup to reach your device. GCM is only used for notifying the device there is a message on Signal servers.
You can also disable permissions on the Google Service Framework and use something like XPrivacy for MUCH more explicit permission control (revocation, spoofing, etc...) if you still want GApps on your device.
You can also disable permissions on the Google Service Framework and use something like XPrivacy for MUCH more explicit permission control (revocation, spoofing, etc...) if you still want GApps on your device.
[0] https://microg.org/