Not that GrapheneOS does not need to trust the hardware we evidently do by releasing our OS on and using it.
As anyone would have to, along with the OS in choosing to use it, just as with any hardware/software. However I was referring to trust that it hasn't been compromised.
The simplest way is to direct you to our features page:
https://grapheneos.org/features
As well as how we use Hardware attestation to ensure the system has not been tampered with, info for which can be found here:
The majority of which is only possible with the industry leading secure hardware provided by the Pixel platform.