On Fri, Oct 18, 2019 at 2:11 PM Kévin Bois <kevin.bois@biblissima-condorcet.fr> wrote:
[...]

You raised the right issue : I've checked in chrome's console, and the XHR sent is : "?action=opensearch&...". Do you know how can I set the search box to use the wbsearchentities API ? I don't remember seeing this option or disabling it anywhere.

Unfortunately I don't know how this is activated, if we are talking about the search box available top-right (using the Vector skin on rtl languages) then I thought it was activated by default. If you are talking about other search boxes like the main one in Special:Search then it's not enabled there because not supported IIRC.
I'm not very familiar with wikibase internals therefor I can't help much on this issue, sorry.

David.