In Searchanise, accented letters and their unaccented counterparts are considered completely different characters. That is fútbol and futbol are two different but very similar words.
We have done so on purpose due to demand from our European users, for whom accents do matter and must be considered separate letters. This cannot be made an option since it's a server-side setting.
If you want the words fútbol and futbol to count as the same word and point to the same product, there are 2 things you can do:
Make them synonyms in the Synonyms tab
Point them to the same product in the Promotions tab. For example, if a product called Mesa de futbol has the word fútbol assigned to it, it will be found by both futbol (because it's in the title in the title) and fútbol
The both mentioned features are available to all Searchanise Pro subscribers. You can upgrade to Pro in your Searchanise control panel.