blog.crox.net

I found a working procedure here:

- Make sure both EFI partitions are mounted from /etc/fstab, eg. using /boot/eficopy in addition to /boot/efi. (Both partitions need to have the proper partition type GUID, i.e. C12A7328-F81F-11D2-BA4B-00A0C93EC93B or "EFI System".)

- Run dpkg-reconfigure grub-efi-amd64 and include both partitions when prompted.

Add this line to /etc/apt/sources.list:

deb http://deb.debian.org/debian bookworm-backports main

Run:

# apt-get update
# apt install -t bookworm-backports libheif1

This solves the issues encountered when decoding HEIF (.heic) files produced by iPhone / iOS 18, causing for instance rendering in Nextcloud to fail.

This page has more details on using Backports.