Change the default keyboard input when logging into macOS Big Sur Since upgrading to Big Sur, my default keyboard input during the login screen is always 'U.S.'. I need to manually switch it to 'French'.
Is there a way for me to set 'French' as defaut?
In fact, I do not even know where this 'U.S.' input comes from.
Here are my Big Sur regional configurations. They are as I want them and work fine once I am logged in.

The primary language is 'English (UK)'. All menus and system messages
are in English.

The region is set to 'France (custom)'.

The keyboard primary input source is 'French'. I have other input sources, such as 'Russian - Phonetic', that I switch to occasionally.
I do NOT have any English language input source, including 'US'.


To sum up:
all my regional, keyboard and input settings in Big Sur works fine EXCEPT during log in, when the default layout is wrong.
Thanks in advance in helping solve this problem.
PS:
The following link suggests a solution for the very same problem but it dates from 01/2014 and it's solution does not work with Big Sur.
https://vkritis.blogspot.com/2014/01/change-default-keyboard-of-osx-login.html
If you have FileVault activated and are struggling to set your desired language on the login screen try the following:

Turn off FileVault
In terminal execute this to copy your keyboard settings to the login screen sudo cp ~/Library/Preferences/com.apple.HIToolbox.plist /Library/Preferences/
Turn on FileVault again
Reboot

Tested on Big Sur