RESOLVIDO!
Finalmente consegui resolver isso. Vou escrever o que fiz.
sudo rm /var/lib/pacman/sync/*db.sig*
Editar & comentário:
sudo nano /etc/pacman.d/mirrorlist
## Germany
Server = http://archlinux32.vollzornbrot.de/$arch/$repo
Server = https://archlinux32.vollzornbrot.de/$arch/$repo
Server = http://mirror.archlinux32.org/$arch/$repo
Server = https://mirror.archlinux32.org/$arch/$repo
# note: you need to resolve via openNIC (or similar) to access the next mirror
#Server = http://mirror.archlinux32.oss/$arch/$repo
Então:
sudo pacman-key --init
sudo pacman-key --populate archlinux
sudo pacman -Syy
sudo pacman -Syyu
Feito!