According to the Arch Wiki : <https://wiki.archlinux.org/index.php/I3#Launching_programs_on_specific_workspaces>; that seems to be the correct behavior.
You are assigning chromium to be launched on tty1.
No, I am assigning chromium to be launched on WORKSPACE 1 !!
I apologize I just caught the error myself as your email came in. Does i3 require xorg-xserver, and if that's the case, is there already a running instance of the xserver on TTY1(you mention you have mate).
Even if I boot directly into i3 in tty1, chromium is not started on workspace 1. Furthermore, my keyboard is US, not the one I use. Part of my /etc/X11/xorg.conf Section "InputDevice" Identifier "Keyboard0" Driver "kbd" Option "XkbLayout" "ch" Option "XkbModel" "pc104" Option "XkbVariant" "fr" EndSection All my issues seem tied to a xserver issue in fact.