Thanks Josko!
I used the boot image on Friday and it appears to be a bug in boot.iso. When you boot in non-UEFI mode from a USB stick the installer will crush if you try to change the repository mirror. I managed to complete installation with the default options.
Updating wiki will be also useful as it still points to 8.4 boot.iso. Cleaning obsolete stuff even better. I could help but I don't have the credentials. I work for Carnegie Mellon University so getting an account for me might not be possible.
Best,
Predrag