When I try to filter a non-English language post I’ve found that frequently the instance I wanted blocked is not what’s added to my block list.
For example, when I try to block the following instance it’s adding mastedon.social instead of OP’s instance lemmy.eco.br: https://mastodon.social/users/ademir_lemmy_br/statuses/112058841341083344
But the link in the post is to a status from mastodon.social, so if you just go on that link and say block instance the domain it’s on is not the Lemmy site. You should be able to go into blocked instances manually and add lemmy.eco.br there though.
Under settings you can add it there directly.