Why are you avoiding Higurashi just curious? It's far more vanilla than Umineko.I have not watched or read Higurashi (though I have limited snippet knowledge due to it being somewhat notoriously famous.)
Umineko can still be read without Higurashi. Though there are some dabbling references and teases left on the open. But those conversely made me get somewhat interested in Higurashi, despite I previously (some 13 years ago) swore I'd stay the hell away from it.