I wonder if Canonical (and/or Debian) provide any sort of guarantee that all packages in main and universe repos are always either built from source by themselves, or verified by them (in case of deterministic or signed reproducible builds) as opposed to just including binaries compiled by others (which implies that you have to trust them, as well, to not be doing something shady or unclear on their compilation process, or using anything outside the public source repo other than private keys for signing, where applicable).
What are Debian and Ubuntu's policies on this? Do they have any official pages or statements on this matter? I'd expect them to do it at least for main, but what about universe? Who am I "trusting" (to provide what they claim to have compiled) when I install something from universe? Just Canonical/Debian or also the authors themselves?
Related: (some info I found on reproducible builds, mostly old)
- Will Ubuntu work with reproducible builds?
- Are Ubuntu builds deterministic? Why not?