How do I launch a native app via a deep-link in Slack from the Slack API?

I’d like to launch the RingCentral App for MacOS by clicking on a link (or perhaps a button). I can’t seem to get Slack to recognize it as a link.

Here’s my payload:

{ 
  "channel":"dev",
  "username":"DEV",
  "blocks":[{
      "type":"section",
      "text":{ 
        "type":"mrkdwn",
        "text":"<rcapp://r/dialer?number=<phone number> | Click me >"
      }
    }]
}

I’m generally using the Slack API to send plain text messages, nothing fancy.
Using PHP to generate the payload and send to Slack.

Any help is appreciated!

RingCentral URI Scheme