HomeAssistant and OpenHAB are good places to start. I don’t know too much about OpenHAB, but for HomeAssistant you can do almost everything locally.

ESPHome is a good example of a project that they fund where you can use ESP8266/ESP32 devices to create several sensors and other devices for local IoT. They also have a number of ways to bypass cloud requirements for Tuya based devices, Phillips Hue, etc.

Plus this year is “Year of the Voice Assistant” and they’re working on enhancing a locally accessible and hosted voice assistant that doesn’t require cloud access.

Since I am on the same journey as OP and tried it just recently, I have one thing to add about openHAB:

It does not come with actual login credential handling. If you want to make your smart home accessible from outside your home network I cannot recommend openHAB.

I am currently going with Home Aisstant mainly for that reason.

Very good point. HomeAssistant offers a paid service called Nabu Casa that provides you a secure way to access your entire HomeAssistant instance, including cameras, sensors, you can set up mobile push notifications, and more.

Thanks for the hint I did not know about Nabu Casa.

Although I am not clear about the benefit of the service. I thought I could achieve the same kind of access with simply forwarding ports 80 and 443 from my router to my home assistant. Is there anything wrong with my intended setup?