Somehow you have end up with arch mirrors, possibly arch pacman as well.
Your /etc/pacman.conf should have the following repositories :
system -->mirrorlist
world -->mirrorlist
galaxy -->mirrorlist
extra ==> mirrorlist-arch
community ==> mirrorlist-arch
example:
[world]
Include = /etc/pacman.d/mirrorlist
.
.
[extra]
Include = /etc/pacman.d/mirrorlist-arch
Rename the mirrorlist you have shown to /etc/pacman.d/mirrorlist-arch
create a /etc/pacman.d/mirrorlist with the following content:
# Artix mirrors
Server = http://ftp.ntua.gr/pub/linux/artix-linux/$repo/os/$arch
Server = https://mirrors.dotsrc.org/artix-linux/repos/$repo/os/$arch
Server = https://artix.wheaton.edu/repos/$repo/os/$arch
Server = https://mirror.clarkson.edu/artix-linux/repos/$repo/os/$arch
Server = https://ftp.cc.uoc.gr/mirrors/linux/artixlinux/$repo/os/$arch
Server = https://artix.unixpeople.org/repos/$repo/os/$arch
Server = https://artix.rw-net.de/repos/$repo/os/$arch
Server = https://mirrors.tuna.tsinghua.edu.cn/artixlinux/$repo/os/$arch
Server = http://www.nylxs.com/mirror/repos/$repo/os/$arch
Server = https://ftp.sh.cvut.cz/artix-linux/$repo/os/$arch
Server = https://mirrors.nettek.us/artix-linux/$repo/os/$arch
Server = http://mirror1.artixlinux.org/repos/$repo/os/$arch
then pacman -Syyu
# pacman -Ss libphobos
community/liblphobos 2:1.14.0-2 (dlang dlang-ldc)
A D Compiler based on the LLVM Compiler Infrastructure including D runtime and libphobos2