Note that postmarketOS is proper Linux. It runs almost-perfectly (sans camera) out-of-the-box on most Duets, and has for a while. Once you enable developer mode in ChromeOS, the install process is just like a PC laptop. The article seems like more of a sidequest to (promote AI and) install Ubuntu specifically by getting uboot and a UEFI environment, but postmarketOS doesn't need that because it can boot from ChromeOS' bootloader. Installing postmarketOS on my Duets (homestar and wormdingler) was probably the best decision I've made with those devices, and they might be some of the best arm64 devices of that form factor to run Linux on.