Good news but misleading headline: they just added trusted boot with TPM’s. That’s the accepted term for this. Tamper-evident hardware usually means physical modifications get detected to some degree. The TPM itself is probably tamper-evident or -resistant hardware. Plus, many smartcards and all HSM’s. Here’s the only tamper-evident/resitant PC I know of that’s not a five-digit HSM.
Purism is really good at their marketing, and they depend on that a lot. They’ve been criticized quite a bit in the past, but they have done some good in their work with Intel ME. The Intel platform is so locked down it’s impossible to get a truly open system like Stallman has with his ancient Thinkpad. Purism is probably the closest to an open x86 you can get with modern hardware in laptop form.
That being said, I can’t really justify buying one. I can buy a cheaper Dell or HP with better hardware that runs Linux entirely out of the box with a recent kernel and the linux-firmware package. If we had better standards for ARM (manufactures that did ARM+UEFI or device trees that weren’t more broken than Apple’s APCI), we could potentially see more open ARM laptops, but that not-an-architecture needs to stop being unsupported SoCs with shitty drivers before they’ll be taken seriously.