Install
This is the repository archive. It installs, but the folder name will carry the branch suffix and updates will not flow.
Install straight from GitHub with WP-CLI:
wp plugin install https://github.com/kntnt/kntnt-disable-old-slugs/archive/refs/heads/master.zipNo built-in updater. New versions won't appear under Dashboard → Updates. Install new releases yourself, or let Git Updater track the repository.
Kntnt Disable Old Slugs
WordPress mu-plugin that prevents WordPress to store and use an old slugs of posts.