How do I clear my data from a smart home before I hand over the keys?

There is usually no true whole-house reset unless everything is under one ecosystem, so in most cases you do need to clear it device by device. I would remove each lock, camera, thermostat, hub, and doorbell from the app first, delete old user codes and automations, clear any stored video or cloud subscriptions, then factory reset the devices before closing. After that, make sure the hubs are wiped, Wi-Fi is changed, and test from your phone while away from the house to confirm you no longer have access. It is a little tedious, but it is the safest way to protect both you and the buyer.