You can’t verify that even on an open OS as there will still be closed hardware blobs. At least with popular systems there’s a lot of state level hacking activi

You can’t verify that even on an open OS as there will still be closed hardware blobs. At least with popular systems there’s a lot of state level hacking activity so zero days get patched routinely. Also Apple has a program for researchers where they get more access to the system (That program was criticized heavily though for the way it was implemented). It’s not a perfect system so right now you still have to trust someone at some point in the chain.