I wrote a TL on the subject some time ago - you can see in my signature. It got quite extensive with a Republican (and somewhat anti-Lusitanian) Brazil arising from a coalition between the elites of the Southeastern and Northeastern regions, heavily influenced by Great Britain. ITTL, the coming of the Braganças to Brazil is avoided altogether, and a fledling movement for autonomy increasingly becomes a movement for independence after the blundered attempts of the Portuguese of restoring the status quo ante provoke the Brazilians into rebellion.
My POD is pre-Peninsular War, actually, but the divergences are nonetheless heavily affected by the Peninsular War and by the French occupation of Spain.
I find the Peninsula War is actually a good POD, because IOTL it was a very important (not the only one, obviously) catalyst for the independence of Hispanoamerica, notably in Argentina and in Mexico, and then on Colombia. I figured that with some "tweaks" we could have Brazil come as a Republic much like what happened in Argentina or in Chile.