That’s not a good decision to use it. It’s obsolete. (my mind)
Even with my installed arco it no longer worked properly.
Too old → result was sometimes error and some other curious stuff.
I uninstalled it last year.
And sorry Arco Linux is history, of course it`s possible to use this os but …
Back to roots, pls 
Use terminal, pacseek, paru, yay and of course garuda-update. (+ uncomment skip mirrorlist inside /etc/garuda/garuda-update/config; my mind)
Use reflector-simple or use the alias over bash / fish to have a optimized mirror list.
example for fish alias:
alias mirror 'sudo reflector --country United States --latest 5 --age 1 --delay 0.25 --fastest 5 --protocol https --sort rate --save /etc/pacman.d/mirrorlist && bat /etc/pacman.d/mirrorlist'
Here inside forum you can find more from them (example)