Comment by slimsag

Not true. Good luck exporting the issues, pull requests, comments, discussions, wikis, etc. and bringing those to another platform.

Ironically (and I am not defending them), Slack[0] is the only one of the three that has an official way to export all messages. GitHub does not, unless you're counting their API, but then maybe you want to consider Discord things like this[1]?

[0] https://slack.com/help/articles/201658943-Export-your-worksp...

[1] https://github.com/Tyrrrz/DiscordChatExporter