Is there a way to display simple table footer not managed by the library? => no column summary, no formatting, ... Just a simple footer with multilines and static text.

Use Chrome or Edge browser Open a website that uses the CSS attribute "display: table" to create a layout table for visually positioning the content. For example: This website uses "display: table" to ...

AFAIK, CSS cannot affect the DOM tree. So, display: none just says the element should not be displayed, not that it should cease to exist. Style/structure separation and all that.