The RebornOS installer (cnchi) makes use, to know the state of the mirrors, of Uptimerobot and its RSS function. This at the moment is not working, so in the screen of selection of mirrors, select "Manage the mirrors lists manually (advanced)":
With this we solve the problem, until the automatic function is again available.
Thanks for this work around Rafael. I've tried to install Reborn several times yesterday without success. Once I switched to Manual mirror sort Reborn installed successfully first time. The download speeds were extremely slow - I don't if that's because I didn't sort the mirrors or an Internet connection speed problem somewhere. Regardless, I now have a working KDE Reborn installation
Thanks again Rafael.
Old age and treachery beats youth and skill every time.