Press “e” on the grub screen to edit your boot parameters.
(If you’re using Manjaro’s “quiet boot” option, you will have to press the “esc” key to view the grub menu; highlight the “Manjaro Linux” selection, then press “e” to edit the boot parameters)
Find the line that starts with the word “linux” and append the letter “s” at the end of that line (with a space before that letter “s”).
(Just the letter “s” will do - or you can use the full “systemd.unit=rescue.target” parameter)
For example, the line will end up looking something like:
linux /vmlinuz-linux root+UUID=blahblahblah rw quiet log_priority=3 s
Now press F10 (or Ctrl+x) to boot.
You will be in rescue mode, which is all text - no GUI.