I have IKEA Trådfri (which is ZigBee-based). While the hub does connect to the internet for software updates (using ethernet - no WiFi, and no WiFi password to update), there's no "cloud" component. You can't create an "IKEA account", even if you wanted. If IKEA went out of business tomorrow, my switches and bulbs would keep working. I like that approach a lot.
It would be perfectly feasible to leave the IKEA hardware in the house if we were to move.
It would be perfectly feasible to leave the IKEA hardware in the house if we were to move.