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.

Edit: If you’re a DIY kind of person like I am, HomeAssistant offers compatibility with a number of other projects like presence detection via ESPresence, custom firmware for ESP32Cam via Tasmota, WLED for controlling RGB lightstrips and matrices, lots of 3D printing opportunities too. I found it a lot of fun to go through my home and find ways to make things work. Blinds, accent lighting, automations based on time and other factors, etc.

Plus the hardware requirements for HomeAssistant aren’t that high. You can run it on an RPi4b with 2/4/8GB RAM (I would suggest at least 4), a VM that you can expand later and so forth.

Another vote for home assistant. It is not just the best FOSS option, it might just be the best option altogether.

Some advice, think carefully about what you want to achieve with automation before you start. Take some time to draw up what you are going to do before you buy anything. Think about extensibility and don’t force yourself to lay out big money and time all at once. Will Smith (tested.com, tech pod, not Independence Day) recommends doing one room at a time and focusing on spaces that are primarily yours first.

Things to consider: If you live with other people, it might be wise to make everything transparent. Meaning the light switches still turn the lights on and off on demand etc.

Wi-Fi is sort of a poor solution to communicating with devices, especially ones that don’t have access to mains power all the time. Consider if you are going to deploy zigbee, z-wave, or a matter mesh. Matter, being very new would be challenging but it is clearly the future of low power wireless communication for home automation.

Set a goal that NOTHING requires a external service or internet connection and stick to it. That might mean giving up on some types of devices but it’s YOUR house, not google’s.

Think automation first. Phone and voice control is cool. But having things just happen the way you would want without have to do anything is even cooler. Be smart about complexity though. How would things have to change if your partner started working a different schedule for instance?

Finally, get creative. Lots of silly problems can be solved with this technology. My favorite automation turns the damn hot glue gun off after 30min so my kids don’t start a fire if they get forgetful after a craft project.

https://lemmy.world/c/homeassistant

https://community.home-assistant.io/

Amazing community, lot of guys there prefer local (non-cloud) services

Everybody else is already talking about homeassistant. I'm going to add that there are zigbee, z-wave, and rarely bluetooth based alternatives for almost all of the nest/alexa/etc accessories, and those work through a local hub.

You should look into Home Assistant, it's really good at managing local and cloud services

I would suggest you to use Node Red as backend and Home Assistant as frontend. With Node Red you have a very robust system that survives years of updates without problem (I've been running for...mmm...maybe 7/8 years and no update have ever broken anything, while I read all over stories of Home Assistant breaking over updates). Node Red has node for about anything, you can make your home automation product/brand independent using MQTT, so Node Red collects all the sensors/actuators and sends to HA what's needed. If tomorrow you'll change a device, all you have to do is connect a couple of nodes and use the same MQTT topic as you did with the previous device (I don't know if I explained myself...sorry!) If tomorrow you'll want to switch from HA to something else, it will be pretty easy with Node Red in the back! All of this, clearly, IMHO!

I’d recommend waiting a bit. Thread (network) and Matter (protocol) are finally gaining traction, and is poised to become the de facto standard across all major platforms (Amazon/Apple/Google). Buying Zigbee/Zwave/WiFi/BT gears now is literally buying gears that’s going to be outdated immediately.

Once you get interoperable devices on the better standards, you’d then be able to layer on with all-local setup easier.