In England (in my experience) you provide an inventory of what is and isn’t staying (often with an offer to sell some white goods etc). If you take stuff that’s physically attached and/or wired in, the purchase contract will require the vendor to make good any damage.
For instance when buying a previous house the vendors wanted £100 each for the really ugly wall sconces. We declined and so were left with terminated wires where we could fit our own lights. I don’t see why smart home components would be any different provided you made good with basic switches and valves.