Does real-time collaboration only work with Sketch Cloud? Or can I use it with other hosting alternatives (Box, Dropbox, etc)?
Real-time collaboration is available in beta as part of version 71 of the Mac app. We’re slowly rolling out this update to everyone so if you haven’t been prompted to download it just yet, don’t worry — it will be available for you soon!
While you can store copies of your documents in third-party Cloud services in order to share them, real-time collaboration only works for documents in your Team’s shared Workspace.
We want to ensure that the correct people are accessing your documents. If you want to invite external users to collaborate on a document with you, you’ll need to invite them via email through your Cloud Workspace with Edit permissions. Note: both the owner of the document and the person collaborating need to have a valid Sketch license or subscription.

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