Old x64 laptops are great, and I've certainly used one as a router before, however they do have drawbacks (cooling profile is usually shitty for 24/7 use, and they often don't love to be stripped from their shell, lose their display and etc). A laptop generally does not have all the peripheral chipsets and connectors you want and usually has extra stuff you don't want.
For $120ish I'm not sure you could beat the value prop of one of these boards with a used laptop. Supply is certainly an issue and was even before COVID. Waiting until 2022 sucks, but I'd argue they are by far the best overall option for a DIY whitebox router I've personally seen.
I don't think there is a problem with stripping it from the display (I dont think its necessary or even desireable most of the time for negligible space differences), it comes with a free UPS and is usually "free"), the idle power consumption is rather low (x240 with screen on is 4w on idle http://forum.notebookreview.com/threads/which-lenovo-laptop-...) my requirements for a device are way lower than those devices listed. I sometimes think of devices such as whiteboxes as marketed tools, like the smart clocks that just look like stripped phones to me, or VR that are just dual phone screens.
For $120ish I'm not sure you could beat the value prop of one of these boards with a used laptop. Supply is certainly an issue and was even before COVID. Waiting until 2022 sucks, but I'd argue they are by far the best overall option for a DIY whitebox router I've personally seen.