What is the best privacy-focused home security system?

I do not need my security system to have WiFi and Internet access (Ring), nor do I need it to have a central hub with an always-on cell signal (Simplisafe). I don't trust these companies with me and my family's data, the same way I don't trust all these free Google Home and Amazon Alexa hubs with my data.

Any recommendations? Any open source security system projects with open source hardware?