argante
Could you explain and justify this further?
Okay, we'll do that below, but we're close to removing the thread now. It's wasting the time of the project and it's filled with misinformation
modifying an old x230 laptop
This is the direct opposite of a secure device.
meaning, instead of OpenSMTPD, I have smtpd from the usr.sbin/smtpd repository
Doesn't support authenticated encryption (DANE or MTA-STS) among other things. It can't do it natively or via external implementations.
argante
You don't need LibreKey/Nitrokey or heads to validate the BIOS and operating system.
These don't do that in the first place.
All you need is a small hardware-encrypted USB drive with a read-only switch.
Even if you're fully booting off this, it doesn't protect the firmware and other state on the device.
Install a custom version of the Linux kernel with basic tools, your own statically linked copy of mtree to scan system files, and a flashrom for BIOS validation.
You can't meaningfully validate anything in these things this way. It depends on the incorrect assumption that you have a secure way to chain trust to what's on this USB drive and that scanning things that way would be secure which it isn't.