Butterfly away the gold discovery in Minas Gerais as the discovery changed the course of Brazilian history where until then, it was dominated by Northeastern sugar interests with lesser interests of recruiting Portuguese settlers as they had to rely the slave African and the Tupi labor for their survival.
Without the gold in Minas Gerais you would't have Brazil in OTL form....the gold run to Minas Gerais was pivotal to the integration and development of the Portuguese South American Colonies as an united nation...until them, you had three distinctive colonies: the Northeast, with a sugar based economy and closer links with Portugal, the Southeast, poor and underdeveloped, that lived of enslaving native tribes and constant territorial disputes with the Spanish colonies of Paraguay and Rio de La Plata and the Amazonic North, where population was sparse and a indigenous portuguese-native culture started to develop in the XVII Century.
Without the gold of Minas, you butterfly the exodus of the Portuguese Royal Family to Rio de Janeiro and you keep the division of OTL Brazil in three large blocs...those blocs would split in similar ways as the Spanish colonies did during the Independence Wars of 1810s / 1820s.
Given the closer cultural links with Portugal, the Northeast would keep Portuguese as the main language, with Bahia maybe having african dialects much more present than OTL....the North would also adopt Portuguese as a unifying language given the spread of the country (somewhat close to 50% of OTL Brazil land mass) and the absence of a strong Tupi presence in Amazonia.
The best shot for Tupi would be the Southeastern nation, especially in OTL Sao Paulo, Paraná and Mato Grosso do Sul state...here you could end with a situation close to OTL Paraguay, where Portuguese would be the "formal" language but Tupi being used daily....in fact, the colonial Sao Paulo was already developing a Portuguese - Tupi creole called "Lingua Geral Paulista"...maybe this would be the second language adopted by this nation after independence.