This is really inspiring I have been dreaming of building my own little portable notebook, powered by PI4 and a hefty USB-C battery. With the beautiful, small HDMI LCD panels available today and a 3D printer, its within reach!
Depending on your goals, there's the GPD Micro PC [1]. Quite the odd duckling, but it includes an RJ-45 and an honest-to-god DB9 for RS232! Not nearly as fun as building it yourself though!
100% inspired by https://habr.com/en/post/437912/ which I first saw here on HN