In the Slack API docs, there are plenty of arguments for chat.postMessage, including unfurl_links:
https://api.slack.com/methods/chat.postMessage

However in this SDK there only a few arguments documented:
https://slack.dev/python-slack-sdk/api-docs/slack_sdk/web/client.html#slack_sdk.web.client.WebClient.chat_postMessage

Overviewing the source code, it seems to forward the arguments to the API:
return self.api_call("chat.postMessage", json=kwargs)

Does it actually work or the arguments need to be manually mapped?

If so, may I contribute with a pull request?