Why does alt+left arrow go into tty now? That's a chrome shortcut for 'back' and it keeps taking me to tty or login screen

I'm using 18.04.1 LTS. I looked at the related questions, but they seem to suggest that Alt+Tab is also affected and somehow related, which is not the case for me.

This is a known bug. See Alt+left/right arrows switch between tty consoles (Gnome Shell vanishes), cannot disable for details.

For what it's worth, the same thing happens in Firefox.

This command solves my problem.

sudo kbd_mode -s

Without argument, kbd_mode prints the current keyboard mode (RAW, MEDIUMRAW or XLATE). With argument, it sets the keyboard mode as indicated:

-s: scancode mode (RAW),

-k: keycode mode (MEDIUMRAW),

-a: ASCII mode (XLATE),

-u: UTF-8 mode (UNICODE).

Source:

man kbd_mode

sudo kbd_mode -s

This fixed alt+arrow tty problem for me on ubuntu 18.04.2 with Firefox 66.0.3.