As you may know, Slack portable has been removed from Portapps. This follows the discontinuation that occurs on June 10, 2019.

However I received again a letter for intellectual property infringement because material elements were still present on the website and the GitHub repository. That’s why the references to Slack portable have been removed from the website and GitHub.

You can always build Slack portable yourself using the source code available in Instructions for building a portapp are available on the Contribute page.