Shortcodes showing in excerpt despite using strip_shortcodes

So, as iguanarama pointed out, the first step is to make sure that the theme you are using uses the_excerpt() to show the excerpt.

You’ll want to go check in your archive.php file how it is displayed. In my theme it was using the file 'template-parts/content-front-c.php'. Then go to this file and see what is the function displaying the excerpt. Right after the function gets the content, add $content=strip_shortcodes($content);, and, in my case, it worked !