>An Open Source phone would only be actually beneficial if there will be an automated transparent and trusted global support infrastructure for it that would require zero user interaction.

I think that's a given except for the zero interaction. Even my android phone alerts me of updates. Anyways, you make it sound like it's nearly an impossible task, but nearly every day my ubuntu laptop alerts me of updates and then updates in the background far more seamlessly than my windows workstation. Plus the distro has over 4 years of support. This is something linux distros figured out years ago.