Technology

When something similar happened in the UK, it was pretty much exclusively smaller/niche forums, run by volunteers and donations, that went offline.

[Warning, IANAL] I am really not sure if the experience is transposable for two reasons:

1. UK follows Saxon tribal law, while Brazil follows Roman civil law. I am not sure but I believe the former requires both sides to dig up precedents, and that puts a heavier burden on the smaller side of a legal litigation. While in the later, if you show "ackshyually in that older case the defendant was deemed guilty", all the judge will say is "so? What is written is what matters; if the defendant violated the law or not.".
2. The Americas in general are notorious for sloppy law enforcement. Specially Brazil. Doubly so when both parties are random nobodies.

So there's still a huge room for smaller forums to survive, or even thrive. It all depends on how the STF enforces it. For example it might take into account that a team of volunteers has less liability because their ability to remove random junk from the internet is lower than some megacorpo from the middle of nowhere.

Additionally, it might be possible the legislative screeches at the judiciary, and releases some additional law that does practically the same as that article 19, except it doesn't leave room for the judiciary to claim it's unconstitutional. Because, like, as I said the judiciary is a bit too powerful, but the other powers still can fight back, specially the legislative.