Ok found some more info.
I did another fresh install with Cinnamon instead of Gnome and ran into the same problem. The only thing I didn’t do was disable some of the mirrors in antergos-mirrorlist. I tried again with Cinnamon, after disabling almost all of the mirrors as I did the first time I got it to work. I left only the top two United-States mirrors and the Canada Mirror. I disabled all of the others. The installer functioned correctly.
My guess is that there is a problem with one of the mirrors and Cnchi currently isn’t handling it as expected. Cnchi 0.14.106
Same here: just USA and Canada mirrors and installed at first try.