I had probably written a longer comment earlier on HN, but if anyone is looking at this and is waiting for the perfect laptop... don't. (Assuming you have the money & time, I unfortunately do not right now.) The catch is that you would need to have moderate levels of proficiency with mechanical and electrical skills.
At the end of the day, commercial clamshell laptops...
1. Have terrible ergonomics, due to the small distance between the keyboard and the screen (unless you're a baby, in which case, hi!). The small screen size doesn't help unless you're okay carrying a 17" laptop around.
2. Have components that will fail due to hardware wear and tear. Most noticeable are the hinges but also USB/audio ports and sometimes keyboards. Be it gunk or an accidental pet dropping the laptop on the port.
A few companies occasionally try to address [1] - like the Asus Easel or the Lenovo/Asus folding laptops that improve portability or screen angle/position. Framework laptops address [2], but are traditional clamshell.
If you truly want a solution,
a. Choose a decent single board computer (SBC) as a base, like a gigabyte brix.
b. Print a 3d case for it to make it as small as possible.
c. Spin your own display from panelook.
d. Attach case from (2) with an expanding hinge-type contraption.
e. Embellish with desired parts. I'd suggest framework expansion cards.
f. ???
g. Profit!
(It doesn't hurt that 4"*4" and VESA-compatible SBCs and miniPCs are often standardized at least in 2 dimensions. And if anyone's interested in anything more on this front - making one, selling it, making a business of selling it etc - feel free to reach out to me (email in profile). I'm frustrated with modern laptops and fortunately have a degree in mechanical engineering.)