On Pixel and Nexus, yes. for every other device it would require coop with the device manufacturer: they build the open-source code (+ their own proprietary ext

On Pixel and Nexus, yes. for every other device it would require coop with the device manufacturer: they build the open-source code (+ their own proprietary extensions), add google apps and libraries (that are sandboxed) and sign the build. Only they have the private keys to provide updates, Google does not have full device access.