One of my computer science professors from MIT has installed a smart home. I was over for a dinner and he told me a story about how he hit a third-party API rate limit on opening his garage door. Apparently, these things aren't self-hosted for the most part.

I have a pretty deep "smart home" setup and it's all run locally from a laptop in my closet with Home Assistant OS. I have run into 0 limitations. All my devices are kept on their own dedicated Zigbee mesh and/or network separate from my LAN. Only way to communicate in or out is via Tailscale. It's incredibly easy to get started too.