Hi,
Thank you for all the details, it helps us a lot!
I have made a few corrections on the index table configuration, namely I removed the acf-field and acf-field-group post type from indexing, as it does not affect the outcome. I have also applied this custom code to the bottom of the functions.php file in your theme directory, that may help with indexing the ACF relationship fields. Please note that by default that is not supported of indexing ACF relationship fields for compatibility reasons, but hopefully that custom code should do the trick.
The taxonomy terms were already indexed with the product, it was in the results list on the 4th page when searching for “Intérieur”. I have re-created the index so that the fields are also indexed, and did a test search for “intérieur extérieur 3m” to make sure it is working, and it looks like that did the trick: https://i.imgur.com/7QECFyB.png
The taxonomies and the relationship field (at least partially) should be indexed now.
I hope this helps!