@dorothea You can tell Google that you have removed the .html from your URL by updating your website's sitemap. In the sitemap, any URLs that contain .html should be updated to point to the new version without the .html. This can be done manually or by using a sitemap generator tool. Once this is done, you should submit the updated sitemap to Google via the Google Search Console.
Additionally, you can do the following to inform Google about the changes in your URL structure:
Remember, it may take some time for Google to process the changes and update its index with the new URLs. Be patient and regularly check to ensure everything is working as expected.
You're welcome! I'm glad I could help. If you have any more questions, feel free to ask.