При ошибках вроде этих:
error: required key missing from keyring
error: failed to commit transaction (unexpected error)
Errors occurred, no packages were upgraded.
Помогает что-то из этого:
# Archive the GNUPG directories
mv $HOME/.gnupg $HOME/.gnupg.bak
sudo mv /root/.gnupg /root/.gnupg.bak
# This one fixed the GNUPG Error
dirmngr
# Refresh Keys
pacman-key –init
pacman-key –populate archlinux
pacman-key –refresh-keys