I have lots of Tradfri Ikea products. They are officially designed to work offline. Otherwise zigbee and z-wave products mostly work completely offline. Some

I have lots of Tradfri Ikea products. They are officially designed to work offline. Otherwise zigbee and z-wave products mostly work completely offline. Some Xiaomi products (you need to be careful, as not all work offline) work offline and can be connected to local servers. For shutters I use products by Rademacher. Its yet another base station (by now I have 4...), but they can be connected over http locally.