Can't find pull request preview

[jquentin-lion]

I don't understand this paragraph of the documentation about Pull Requests previews.

For every PR done using a target branch synced with a GitBook space, you’ll see a status added to the PR with a unique preview URL. Clicking the Details link on the status will take you to the preview URL for your content.

Where am I supposed to see this status? In the gitbook interface? Github?

I have created a pull request and I don't see any preview button anywhere.

(The synced branch of my gitbook space is main, the PR targets merging into main, my github sync config confirms it does have pull requests read access in that repo)