Requires signal-cli: https://github.com/AsamK/signal-cli and Protocol::DBus to be used as module in FHEM (see in file documentation for more details)
See FHEM Forum (German) for more details https://forum.fhem.de/index.php/topic,118370.0.html
Installer uses binary files from https://github.com/exquo/signal-libs-build
Basic english documentation inlined.
German documentation in Wiki https://wiki.fhem.de/wiki/Signalbot