Just from reading this:
Signal uses Google Play Services to notify devices when new messages are available for you.
This is something not ideal for many reasons among potential privacy threats and the impossibility to use Signal on devices which does not have the Google Play Services enabled or when they are installed but outdated or when user does not want to provide hir Android device a Google account.
As an example, we cannot use regular version of Signal on LineageOS with MicroG. Signal tells us it cannot to connect to the network, ...
You'll find below a download link to get a patched version of Signal which removes Google Play Services support, it allows Signal to work on any Android device you want.
Langis is an unofficial version of Signal and provided without waranty, it is Free Software and we provide you with all the build steps needed to build the APK as we do before giving them to download on that page.
The APKs provided here are signed to allow you to upgrade your Signal App without needing to uninstall previous version.
Tell me that Langis isn't sounding like theatre and marketing...
Signal works fine with or without privileged Google Play, Sandboxed Play Services or MicroG. Where FCM is not available at first use Signal uses websockets for push notifications so long as it is given battery optimisation. Typically recommended around the usual suspects of alternate OSes such as Lineage and /e/, I would avoid.
Molly on the other hand has actual improvements and a complete run down of their feature set:
- Data encryption at rest - Protect the database with passphrase encryption
- Secure RAM wiper - Securely shred sensitive data from device memory
- Automatic lock - Lock the app automatically under certain conditions
- Block unknown contacts - Block messages and calls from unknown senders for security and anti-spam
- Contact deletion - Allows you to delete contacts and stop sharing your profile
- Disappearing call history - Clear call notifications together with expiring messages
- Debug logs are optional - Android logging can be disabled
- Custom backup scheduling - Choose between daily or weekly interval and the number of backups to retain
- SOCKS proxy and Tor support - Tunnel app network traffic via proxy and Orbot
READ ME: https://github.com/mollyim/mollyim-android
If I were to pick one based on the above it would be Molly.