Home Assistant is such a solution. It's quite decently polished and supports a ton of devices. Where devices have local APIs, it uses those, so it doesn't rely

Home Assistant is such a solution. It's quite decently polished and supports a ton of devices. Where devices have local APIs, it uses those, so it doesn't rely on vendor cloud services unless there is no choice. I use it with TP-Link Kasa smart plugs and Broadlink IR blasters, both of which have usable locale APIs, on an isolated WiFi network with no Internet access (it's harder to turn off the cloud stuff for these kinds of things, but as long as I can block it myself I don't care if they try and fail to connect to the cloud).