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
https://wiki.archlinux.org/title/Getty#Add_additional_virtual_consoles

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