I've ported PostmarketOS to the Next Thing Co (NTC) CHIP.
I'm using the downstream kernel from NTC right now, but this device should support mainline uboot and kernel.
Will experiment with mainline uboot and kernel in the next days.
TL:DR this device can't be flashed with pmbootstrap right now, I will put manual flashing instructions on the Wiki.
This device uses a raw NAND instead of an eMMC, so it needs its rootfs to be in UBIfs format.
UBIfs (like JFFS2) is different from regular filesystems because it takes care of flash memory management like wear leveling or bad block management.
Right now I haven't found a way to create the UBIfs image from pmbootstrap, so I will write instructions to do so manually in the wiki page.
Once the UBIfs image is created, it can be flashed using fastboot, which requires putting uboot in fastboot mode from the serial console.
At the moment it is possible to build a pmOS image using the commands explained in the wiki page.
However to boot this image we need to change u-boot configuration, and unfortunately the procedure explained below does not work on all the version of u-boot for CHIP around.
The next step is to package and compile u-boot to provide a uniform bootloader for pmOS.