Home Assistant is open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts. Perfect to run on a Raspberry Pi or a local server. Available for free at home-assistant.io
Ecobee works great, and supports local control via HomeKit. Note that you don't need any Apple devices to use HomeKit, as Home Assistant natively supports HomeKit devices.
Not all features are available via HomeKit as it's just a basic thermostat integration. Ecobee also have an open API with access to all features, but unfortunately their API is all cloud-based rather than local.
I switched out three Honeywell TCC thermostats in the spring with Ecobee. All in all, the Ecobee units are great and work well with HASS. I use the cloud API integration and have some automation that kicks set-back in a bit quicker than 2 hours like the t-stats do natively when we are out of the house.
The only regret I have is I bought the higher end model, but should have bought the cheaper ones - I don't (and won't) use the built-in Alexa, don't need the C wire kit, and the VOC/CO2 sensor is garbage.
The remote temp/occupancy sensors are great and do help balance out temperatures when the t-stat doesn't cover all rooms very effectively.