We had both Simplified category setup and the upcoming change in the admin UI (and probably a what’s new item too):
You should have received notifications about this change both when it appeared on your site and when it was automatically enabled, which is likely only this week when the change was moved to Stable status.
As Kris said, the mitigation is the upcoming change in core, which gives you time to migrate things:
What else would have helped you in this case? We could add some extra details in the upcoming change linked topic with details on what developers need to do to prepare.
As for developer warnings, I can consult with the dev-xp team to see if there is something better we can do next time.
We will fix these today, we must not have had adequate test coverage here, because nothing from these plugins failed when I did DEV: Move enable_simplified_category_creation to stable by martin-brennan · Pull Request #39212 · discourse/discourse · GitHub , but other plugins did:
