I've got category URLs like .*/.html in Magento2. Ideally I prefer .*.html, however I'll settle for .*/.
So I go to the Magento admin and change the preference Stores -> Configuration -> Catalog -> Search Engine Optimization -> Category URL Suffix to the empty string
However with caching disabled and a reindex, the category pages are return HTTP 404(page not found). I've even tried deleting all products and categories, then reloading with the revised setting, but still getting 404(page not found).
Any idea what might be wrong?