I've heard some people speculating that in USUM we didnt just moved in to Alola because the surfoard is outside and the garage is now open so it probably means we've been living in Alola, at least for a while. That would imply that maybe its a sequel or even some other time

However after going through the trailer frame by frame you can notice that the boxes are still on the veranda on the right side of the screenshot. So the mom was probably just a lot less lazy about unpacking. Couple it with the fact that its the very same house and we're picking our starter and we can for sure rule out sequel and the protag being Alola-native.