Comment # 3 on bug 1074295 from Adam Majer

Seems to work for me.

Repository     : openSUSE-Leap-42.3-Oss
Name           : mc                    
Version        : 4.8.15-9.1            
Arch           : x86_64                
Vendor         : openSUSE

I did,

> mc ftp://ftp5.gwdg.de/pub/opensuse/repositories/Kernel:/stable/standard/src
>
> => kernel-firmware-20171221-35.1.src.rpm (select and Enter)
> => CONTENTS.cpio (select and enter)
> => kernel-firmware.spec (F3 to view, worked)

or 

> => kernel-firmware-20171221.tar.xz
> => GPL-2 (F3 to view, worked)

Can you provide sample of what is actually not working?

You also mentioned SFTP but your URL is using FTP instead.