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Looking for quick and easy door sensors
(lemmy.world)
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
If you use Zigbee the Aqara and SONOFF contact sensors are both fairly good in my experience.
The Aqara ones are very small and neat, the SONOFF are a bit larger but cheaper.