Super and arrow key has started switching tty

Your Super key can switch from performing as expected when your keyboard mode switches from raw. (Good explanation of the differences between keyboard modes can be found here). This occurred to me after using the Magic SysRq key to switch the keyboard from raw mode while my system slowed while paging memory.

You can check what mode your keyboard is in with sudo kbd_mode and if it is not in raw change it back with sudo kbd_mode -s. Full info at https://linux.die.net/man/1/kbd_mode

This seems to be caused by an update changing something. A restart should fix your issues, and go back to Super+Arrow snapping a window to half the screen, not changing tty.