Every time I try to install Silverblue on a drive with pre-existing EFI partition (dual booting), I get the message “failed to write boot loader configuration”. The installation log is showing the same above messages, and I confirm the nested directories /boot/efi/EFI/EFI... too. Is this a known bug for Anaconda?
If anyone is interested, this worked for me:
Run this from the shell when the error dialog box comes up, and then ignore the error and continue the installation (replace <deploy_id>.0 with the existing folder):
chroot /mnt/sysimage/ostree/deploy/fedora-workstation/deploy/<deploy_id>.0 /bin/sh
mv /boot/efi/EFI/EFI/* /boot/efi/EFI
rm -r /boot/efi/EFI/EFI
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
exit