Fails to boot after full system upgrade

I should mention my harddrive setup:

  • emmc (mmcblk1): Linux distro that I do not use (the one the pinebook was shipped with originally - some ubuntu or debian).
  • nvme (nvme0n1): Data
  • Micro-SD (mmcblk0): Manjaro

Here is output of lsblk -o NAME,PARTUUID,LABEL:

NAME         PARTUUID                             LABEL
mmcblk1                                           
|-mmcblk1p1  0666f440-01                          BOOT
`-mmcblk1p2  0666f440-02                          
mmcblk1boot0                                      
mmcblk1boot1                                      
mmcblk1rpmb                                       
mmcblk0                                           
`-mmcblk0p1  32c0149c-01                          ROOT
nvme0n1                                           
`-nvme0n1p1  07b3e47f-3b0d-544b-bf4c-6a0afdd7b072 Data

And here cat /etc/fstab from the Manjaro rootfs (on the SD-card):

# Static information about the filesystems.
# See fstab(5) for details.

# <file system> <dir> <type> <options> <dump> <pass>
LABEL=BOOT_MNJRO  /boot   vfat    defaults,noexec,nodev,showexec     0   0

@Keruskerfuerst: chrooting into the system and running mkinitcpio -P is an option that I also thought about when I saw that the kernel on my system differs from the one that is installed on a live-usb-stick. Is there any tutorial on how to accomplish that? I.e. can I follow these instructions: [HowTo] Chroot from or into any Linux distribution

Cheers
Lars