Firstly, This mirror is unofficial, and it's not guarantee anything.
Secondly, This mirror is not my own. Just sharing information.
mirror.premi.st is famous mirror provider on South Korea, and they announced to support archlinux arm mirror on 2020-08. (Korean)
But It's still not official support of mirror.premi.st so this mirror can be shutdown for low usage, or something other reason.
If you want to use this mirror, add below line into top of '/etc/pacman.d/mirrorlist'
$this->bbcode_second_pass_code('', '
Server = http://mirror.premi.st/archlinux-arm/$arch/$repo
')