Notice that Certified Hardware, as it is appears on the Qubes website, requires that the producer of said hardware furnish two non-returnable pieces of the hardware and pay a fee, to the Qubes people, and wait.
Purism makes a 14 inch laptop that has Coreboot, and I am guessing, for several reasons they will not try to get their 14 laptop Certified. I should not explain things I know little about.
But if I had money, they do make a good effort to build a secure Laptop.
and a mini, which relies on USB, which as someone said, has problems in booting, and another potential security hazard.
and a good competitor.
Perhaps one or both the manufacturers has solved the boot problems.
Nitro sells refurbished laptops of an older Thinkpad, which, after being re-manufactured, is well trusted.
Notice that in any laptop, Qubes does not use all the available Cores or is hyperthreading of processors to avoid a Security problem. So using laptops can require patience.
While not good for a business today. I have looked at buying an older tower, or such that uses serial port modems and serial port keyboards to use at home, plugged into mains.
I am guessing when you say 4K, you meant screen size. I have no experience whether one can plug in 4K screen into some of these laptops. I think one of contributors, Sven said he use some kind of monitor with his T430, which he personally upgraded to be the same as the Certified T430 Laptop. But it is another potential Security hazard.