I've tried growing Hydrangea arborescens indoors before. They definitely prefer bright, indirect light, similar to what they need outside. I used a large pot with good drainage and a rich, slightly acidic soil mix to keep the roots healthy. For watering, I kept the soil consistently moist but not waterlogged. During winter, I noticed they needed less water due to reduced growth. It's a bit of a challenge indoors, but with the right conditions, they can adapt nicely. Have you considered positioning them near a south-facing window?