Indeed, but @Nachlese pointed another problem, also solved now
LANG=C sudo pacman -Syu
:: Synchronizing package databases...
core is up to date
extra is up to date
multilib is up to date
:: Starting full system upgrade...
warning: archlinux-keyring: local (20240313-1) is newer than core (20240208-1)
warning: plymouth: local (24.004.60-6) is newer than extra (22.02.122-17)
there is nothing to do