Axolotl

Axolotl is a complete cross-platform primary Signal client, compatible with the Ubuntu Phone and more. Unlike the desktop Signal client, Axolotl is completely autonomous and doesn't require you to have created an account with the official Signal application. There are still bugs and UI/UX quirks and not all Features of the official Signal clients are supported.

It is built upon the go textsecure package and a Vue frontend that runs in an electron/qml WebEngineView container.

Discussion
Personally, for the last few years I have convinced people around me to use Signal instead of WhatsApp. The Signal client for Linux is usable, but not fully adaptive, and needs to be bound to an Android or iOS version with a phone number. Axolotl might present a promising alternative.

Discussion points:
 * Axolotl is currently not available in Alpine Linux/PostmarketOS repos, but on Flathub
 * Whisper Systems LLC has a bad reputation regarding third party clients. Is this really worth the effort?

Installing
Axolotl can currently be installed via Flatpak:

On the PinePhone, it is possible to use the Qt version (built via Flatpack) for text messaging.

Links

 * Porting effort: https://gitlab.com/postmarketOS/pmaports/-/issues/545
 * Someone seems to have a lot of feedback, but performance it not one of them on Mobian on a Pinephone: https://github.com/nanu-c/axolotl/issues/541