Update today broke boot

When you try booting into the system that freezes, have you tried changing ttys? It’s likely that gnome failed to start.
If possible, run garuda-inxi from the system that isn’t working.

Try swapping ttys like this

Agetty manages virtual consoles and six of these virtual consoles are provided by default in Arch Linux. They are usually accessible by pressing Ctrl+Alt+F1 through Ctrl+Alt+F6. 

This should allow you access to a shell even if the desktop hasn’t loaded.

Ignore this, the guide linked below by Duke187 is better.

To chroot into the system with a live usb, you need to mount the main drive then chroot into it like this:

arch-chroot /path/to/new/root

chroot - ArchWiki