Suggestions for modifying the installation guide
I tried to update the documentation myself, but it seems I do not have the permission to do so. So below my suggestions as long as my memory is still fresh:
As first point I would add the point "Enabling OEM unlocking" from the normal CalyxOS installation guide, or refer to it (seems you cannot directly link to that section). "Enable the developer settings menu by going to Settings -> About device and pressing on the build number menu entry until developer mode is enabled. Next, go to Settings -> Developer settings and toggle on the ‘Enable OEM unlocking’ setting."
After point 2
fastboot flashing unlock the phone directly rebooted before I could do an
fastboot flashing_unlock. Suggestion to add something like "reboot again into fastboot and run...". And maybe in general under point 2 that you can abort the reboot by pressing the power button for a longer time (or whatever is suggested).
Point 8 suggest to change it to: "The device should boot into CalyxOS. Don't set it up yet. If it does not power it off by pressing the power button for a longer time. Reboot to fastboot mode again and then run fastboot flashing lock to lock the bootloader. Then confirm that the "unlocked" warning are gone. (Note: Due to a bug in the Xiaomi software, xiaomi will still warn you about an unlocked bootloader; although fastboot will correctly state it is locked)."
I hope that helps. Thank you.