archlinux.org/news/linux-firmware-2025061312fe085f-5-upgrade-requires-manual-intervention/
(略)
this coincided with upstream reorganizing the symlink layout of the NVIDIA firmware, resulting in a situation that Pacman cannot handle.
(略)
first remove linux-firmware, then reinstall it as part of the upgrade:
# pacman -Rdd linux-firmware
# pacman -Syu linux-firmware