Hey @berndgewehr, welcome to Speckle Community.
This has come up a few times, and while the Speckle crew aren’t actively looking at this right now, as I recall, we’ve seen a few companies building their own.
There is one open-sourced contribution I’ve seen from @Zhuangkh that looks in a paused state at present GitHub - Zhuangkh/SpeckleBot: SpeckleBot for Microsoft Teams
I worked on a Google Chat demo a year ago: SpeckleChatBot Webhook Relay