enabled native page publishing in settings (enable page publishing)
created a topic and published as a page at slug ‘about-us’
deleted topic while exploring other page-publishing options
when to re-create the published page at ‘about-us’ via native page publishing (first thing above)
presented with " Sorry, you can’t publish this page. Slug has already been taken. " error despite the fact the page/topic in question has been deleted and is no longer accessible to anyone (including myself, the admin)
Yep, I can repro on Try following the steps in the OP. Currently it appears you need to un-publish the published page before deleting the topic. Ideally, deleting the topic would automatically un-publish the page and free up the slug.
I’m pretty sure this is something we’ll want to improve, but the current workaround would be to find the deleted topic (you can append ?status=deleted to the URL of a topic list to find deleted topics), restore it, un-publish the post, then re-delete the topic.