I stumbled upon this really good article by Splendid IT (German only) https://www.splendid-internet.de/blog/ist-googles-jpegli-wirklich-besser-als-webp/.

According to this article, Google recently came up with a new library to render small but rather good looking images in a regular JPEG format. This is a completely new approach in order to be independent from the mercy of browser vendors.