Try to downgrade mkinitcpio - see
https://forum.manjaro.org/t/failure-to-boot-manjaro-from-legacy-usb-with-btrfs-after-update-mkinitcpio-35-2-2-with-manjaro-22-1-0-1/137624/22
- boot live media
- mount your flash as in brahma’s post above
- chroot
- install downgrade
- downgrade mkinitcpio to 34.2
# pacman -Sy downgrade
# env SKIP_AUTOSNAP=1 DOWNGRADE_FROM_ALA=1 downgrade mkinitcpio
- ignore mkinitcpio updates until this will be fixed …
I made a fresh installation on USB Flash with btrfs and had this issue - when I nstalled on ext4 instead, I could boot after the update. Another user who uses ext4 on an USB SDD had the same failure with his system …