The Verdict: Clear Path
You can apply to the Ministry of Justice to reacquire your original Brazilian nationality. Find the declaration that recorded your renunciation, since its date and terms are the basis of the application.
The October 2023 amendment (EC 131) says in terms that renouncing does not prevent you from later reacquiring your original nationality. What is restored is your status as a Brazilian by birth, not a naturalisation.
One thing we check before filing: whether reacquisition is still being made conditional on giving up your other nationality. The consular guidance says so, but it predates the 2023 amendment.
The documents are those the ministry lists for reacquisition (Annex IX of Portaria MJSP 623/2020).