This may be a really newbie question but I absolutely can’t find it.
When I create a new post, it contains a HTML block, instead of the usual “Start typing” prompt that auto-inserts a paragraph. My users (of course) start typing the article in the HTML window and it does not end well.
Thank you for the screenshot, I’m not able to replicate this, my site is using the Twenty Twenty-Three theme with only Gutenberg active. This may be a plugin or theme conflict, can you do a conflict test on the site?
If you don’t want to affect how others view your site when you are troubleshooting, you can install the Health Check plugin.
It will add some additional features under the menu item under Tools > Site Health. On its troubleshooting tab, you can Enable Troubleshooting Mode. This will disable all plugins, switch to a standard WordPress theme (if available), allow you to turn your plugins on and off, and switch between themes, without affecting normal visitors to your site