As far as I know, there is not an integration for these platforms yet, but I wouldn't be surprised if 3CX added support for one or both in the future.
In the meantime, if you wanted to get this to work now, you could create a server-side service that monitors the extension's presence property using the 3CX Call Control API. I presume that both of these platforms (Slack and Teams) have an API for setting the user status.
The Call Control API will notify your service that a property on the extension has changed. It won't tell you what property has changed, so you will need to keep track of the previous status so you can check whether this is the property that has changed, but you can do it. We do this on our Wallboard tool.
As far as I know, there is not an integration for these platforms yet, but I wouldn't be surprised if 3CX added support for one or both in the future.
Nick Galea said:Roadmap: "We will research and consider adding Microsoft Direct Routing capability for Microsoft Teams, allowing you to make calls from Teams via 3CX. Please note that we are not committing to this functionality yet but we are going to research and consider it."
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.