Tikkie I have a deeply tampered/hacked pixel 10 Pro XL (kernel level).
This is not mathematically impossible, but it's genuinely very unlikely.
Tikkie [I] need to verify everything & anything that can be verified through a trusted channel.
Luckily Google included code in the bootloader that verifies the integrity of the system partition every time the device boots. See the installation verification instructions on the web site, then see the Auditor instructions.
Tikkie java.net.UnknownHostException: Unable to resolve host "apps.grapheneos.org": No address associated with hostname
As indicated by MetropleX, this is not an indication of compromise. Note that, in general, unexpected error messages are not a sign of successful compromise by an expert, because when experts compromises a device they use their expertise to suppress error messages that would tip off a target.