When using full disk encryption, the user is asked to provide the password for the disk during boot.
The keyboard layout used at this point in time of the boot process does not respect the choice of layout that a user may have selected during the installation process or have configured on their system.
The keyboard layout is always set to English (default layout) and as the user will be entering the password thinking that another layout is in effect, it will not be able to unlock the LUKS encrypted drives.
The Anaconda installer does not yet know to tell rpm-ostree to track the keyboard layout config and to add it to the initrd.
Bugzilla report: #1890085
Silverblue issue: https://github.com/fedora-silverblue/issue-tracker/issues/3
In terminal, run:
sudo rpm-ostree initramfs-etc --track=/etc/vconsole.conf