Unable to use DNF on Fedora 28 KDE

[Robbi Nespu]

I just fresh installed Fedora 28 KDE but I got something like th is
when run dnf update. "Unable to detect release version (use
'--releasever' to specifyrelease version)" which need me do define 28
each time using DNF

More: https://gist.github.com/RobbiNespu/0707700cad33c7fd830af0c5a91c3e3c

$ uname -a
Linux robbinespu 4.16.3-301.fc28.x86_64 #1 SMP Mon Apr 23 21:59:58 UTC
2018 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/fedora-release
Fedora release 28 (Twenty Eight)

$ cat /etc/issue
\S
Kernel \r on an \m (\l)

[stan]

On Sat, 19 May 2018 14:39:38 +0800
Robbi Nespu  wrote:
> I just fresh installed Fedora 28 KDE but I got something like th is
> when run dnf update. "Unable to detect release version (use
> '--releasever' to specifyrelease version)" which need me do define 28
> each time using DNF

You could try running 
dnf --releasever=28 reinstall fedora-release fedora-repos
just in case those have inconsistencies.  dnf doesn't seem able to find
the updates repo for F28.  Is there anything odd about entries
in /etc/yum.repos.d/?  Extra repos, missing repos, turned off/on repos?