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Mercurygram | Telegram FOSS with UnifiedPush support.
(f-droid.org)
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
Matrix space | forum | IRC
There are also forkgram, nekogram x, whatevergram... I use negkogram x, in particular, and I don't want to switch to another fork to get unified push but losing other features. I guess forkgram users also stick to its features. Etc.