What model? I've been buying used Thinkpads as of late (all Lenovo) and while I do see a slow quality down-ramp, even the newest are more robust than a similar Asus.

When it comes to x86-64, everything is back-doored, make no bones about it. If you want something less insecure, go get a T400 and libreboot it, or buy an SBC that can run with no blobs.