I am sorry to hear that - it sounds strange - since your installation would boot.
Please see this topic for instructions on how to unlock your partition
[root tip] [recovery] Basic Manjaro Linux Rescue and Recovery
T600 is - according to Nvidia - supported by the open driver.
When you have opened your container and mounted the system - I suggest you install the package envycontrol and ensure your gpu is in Hybrid mode.
I will also suggest that you update the system when you are in the chroot as there was stable snap earlier today. Be sure to read the announcement BEFORE update.
Be sure to verify your GPU driver BEFORE restart. Use the Nvidia Driver Assistant to guide you
nvidia-driver-assistant
You may also edit your configuration to disable plymouth
/etc/mkinitcpio.conf(removeplymouthhook)/etc/default/grub(removesplashfrom cmdline)
Then rebuild you init and update grub configuration
mkinitcpio -P
update-grub