You want the Anti-Interdiction service.
You can also use the warrant canary to cover part of the remaining scenario.
I’m not sure that that is possible. If you can’t trust the hardware supplier then you will have to build the entirety of the computer yourself, components and all.
You can build the software from source, after inspecting the entirety of the source code for backdoors. Obviously easier said than done.
The Librem 14 also has some protection against the malicious compromise of some of the hardware components e.g. WiFi and SSD (and microphone / camera).