Then don't do that?
Install vanilla LineageOS or GrapheneOS with no GApps. Then install Signal from https://signal.org/android/apk/
That doesn't address the criticism that this thread started with:
Unified Push, which works flawlessly on Molly, could easily be implemented in the regular client.
The whole point is that it's unusable without Google services due to battery drain. Meta got it right with WhatsApp and a battery-efficient WebSockets implementation for notifications without Google services, but Signal's implementation is poor.