Not sure if this answers the question you have in mind, but it's easy to migrate your data (users, channels, their membership, message history, etc.) from Slack

Not sure if this answers the question you have in mind, but it's easy to migrate your data (users, channels, their membership, message history, etc.) from Slack to Zulip: https://zulipchat.com/help/import-from-slack https://zulipchat.com/help/import-from-slack (I work on Zulip.)