It seemed like a stand-alone film that happens to take place in the same universe. But that's the thing: Evil Dead Rise initially confirms that it is in the same universe as its predecessors. And that there is room to build off. What exactly does Evil Dead Rise have to offer from previous installments?
In terms of what you should watch before Evil Dead Rise, though, there isn't any hard and fast rule in terms of chronology or continuity. The latest film is meant to simply be another story within the world of Evil Dead, but doesn't necessarily call upon the events of previous installments to build on its narrative.