Ferdium [1] will at least cover Discord/Slack/Mattermost/Teams, if not Signal, iMessage and IRC.

"Ferdi is a hard-fork of Franz, and Ferdium is a hard-fork of Ferdi" [2].

The available services are listed here [3].

[1]: https://ferdium.org/

[2]: https://github.com/ferdium

[3]: https://github.com/ferdium/ferdium-recipes/tree/main/recipes