I am using Signal on GrapheneOS (without Play Services). Unfortunately it uses a lot of battery. There is however a work of it that uses UnifiedPush (FOSS alternative to Google’s Firebase Cloud Messaging which is part of Play Services) called Molly-UP: GitHub - mollyim/mollyim-android-unifiedpush: Molly with UnifiedPush support.
The caveat is that you need a program called Mollysocket running on a computer at all times: GitHub - mollyim/mollysocket: MollySocket allows getting Signal notifications via UnifiedPush.
This can be installed via Docker, for example. I would assume this uses very little CPU, RAM and storage. Is anyone aware of a free VPS where you can host Mollysocket? I know there is no free lunch, but there are free webhosters like Github Pages and Neocities, so perhaps there is a free VPS / docker hoster somewhere?
I just don’t feel like paying a monthly fee “just” for more battery-saving Signal notifications. As long as I don’t have any other hosting needs, that is.