If you install whatsapp business you can setup an auto response to messages telling people you no longer use whatsapp and to switch to Signal.
There's Watomatic. Author claims it doesn't connect to internet even though it has full network access permission, so idk about it. But the code is FOSS. It's on fdroid too.
Hi! Watomatic developer here. The newer version does access internet (Github API) for following reasons: - To show release notes in the app - (in works) To warn users about outdated versions. This is an issue esp in the non Google Play landscape. - (in works) To show recent contributors list in the About section ...
Having access to internet made lots of things easy so thought that was a pragmatic choice :)