What generally happens when an international service refuses to comply with a court order in Brazil is a temporary blocking that must be enforced by ISPs. Often it is DNS blocking, trivial to circumvent. Sometimes IP-level blocking, often also easy (via VPNs).
This often works and rarely lasted more than a day. I don't think I was ever personally affected by one of those blockings when I was in the country.
I don't really remember any case where a large server failed to comply and remained blocked.
EDIT: There are things that were blocked and remained blocked forever, but they're often things like piracy, CSAM sites... which are things that often get blocked even in the USA. Sometimes this is a harsher block directly at the host of the website, either via court order when it's a Brazilian host, or because international laws were broken, or because the host simply complied.
Ultimately, the only thing Brazil can do is take action on entities inside of Brazil. So yes, Rumble could just say on and put the ball back in Brazil's court for them to block Rumble or go after Brazilian advertisers.
I don't know, but the end result of that sounds a whole lot similar to what Rumble's doing right now. Therefore, I'd say that for other websites in similar positions, they could just send Brazil's mad demandz to the junk pile.