I quickly enabled the feature and did some experiments.
While user can independently customize the sidebar through their user settings, I configured it globally to add Announcements, Support and Development as default categories.
From the linked discourse post, it seems like the current hamburger menu will eventually go away anyways so switching to whatever they seem to be moving to is fine with me. It appears they have already received rounds of feedback in September/October/November, so I would think is also not very experimental anymore. From what I have read it appears this new design is the default for new discourse sites, but just an option on existing old ones(?). So another reason I’m fine with switching to it like other discourse sites have done.
The enable sidebar site setting enables the sidebar, which replaces the hamburger menu. When it is disabled, a new hamburger menu is used instead for sites that prefer it find it more compatible with their existing theme customizations.
Also comparing the new sidebar on mobile I can say the new version is a lot better as it uses more of the vertical space. I viewed how the new version looks like on another discourse site with it.
