Bricked phone after u-boot update

[Boern]

I would put Mobian on an SD card and boot from there to fix it. Preferably the latest nightly to see if it isn't a general Mobian problem you encountered (had that happen to me).
Then I would mount the EMMC somewhere. First the root filesystem and then the boot filesystem.

Code:

sudo mount /dev/mmcblk2p2 /mnt
sudo mount /dev/mmcblk2p1 /mnt/boot

Check that dtb, Image.gz and initrd.img point to the latest kernel

Code:

ls -l /mnt/boot

And finally update the boot loader. u-boot-install-pinephone is just a wrapper for u-boot-install-sunxi64 with some additional checks and tricks to find the correct boot drive. We don't want it to find out the boot drive, we want to supply it ourselves.

Code:

sudo u-boot-install-sunxi64 /dev/mmcblk2

I hope that helps.