thefinn93/signald
signald is a daemon that facilitates communication over Signal. It is unofficial, unapproved, and not nearly as secure as the real Signal clients. Issues and MRs are accepted via GitLab.com. There is an IRC channel, #signald on Freenode, for those that go for that sort of thing, or#signald:matrix.org on matrix.
https://github.com/thefinn93/signald?utm_source=tldrnewsletter