nanu-c/axolotl
github.com
A Signal compatible cross plattform client written in Go and Vuejs - nanu-c/axolotl

Thought it was only available for Ubuntu Touch phones but it can also be used on Linux desktop and Mobian.

Excerpt :

Axolotl is a complete cross-platform 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.