I already have koma-script so have had to use koma-script-examples for illustration
You should not attempt to run this type of install command through tlmgr.bat since it has a different specific updater role.
It is better to run tlmgr-gui when you can. In that way I was able to quickly check if koma-script was already installed, this would be equivalent to the first part of your command.
tlmgr info koma-script
That command should confirm if koma-script is already installed (which in my case was confirmed by the feedback line installed Yes)
so in my case I switched to target the example files
\texlive\2018\bin\win32>tlmgr install koma-script-examples
TeX Live 2018 is frozen forever and will no longer be updated. This
happens in preparation for a new release.
If you're interested in helping to pretest the new release (when
pretests are available), please read
https://tug.org/texlive/pretest.html. Otherwise, just wait, and the
new release will be ready in due time.
tlmgr.pl: package repository
ftp://tug.org/historic/systems/texlive/2018/tlnet-final (not verified:
gpg unavailable) [1/1, ??:??/??:??] install: koma-script-examples
[551k] running mktexlsr ... done running mktexlsr. tlmgr.pl: package
log updated: /texlive/2018/texmf-var/web2c/tlmgr.log
\texlive\2018\bin\win32>tlmgr info koma-script-examples
TeX Live 2018 is frozen forever and will no longer be updated. This
happens in preparation for a new release.
If you're interested in helping to pretest the new release (when
pretests are available), please read
https://tug.org/texlive/pretest.html. Otherwise, just wait, and the
new release will be ready in due time.
package: koma-script-examples
category: Package
shortdesc: Examples from the KOMA-Script book
longdesc: This package contains some examples from the 6th edition of the book >>KOMA-Script<<, >>Eine Sammlung von Klassen und >> Paketen fur LaTeX2e<< by Markus Kohm, published by Lehmanns Media.
There are no further descriptions of these examples.
installed: Yes
revision: 47523
sizes: doc: 1665k
relocatable: No
cat-date: 2018-04-23 05:04:11 +0200
cat-license: lppl1.3c
cat-topics: book-ex
collection: collection-langgerman
As you can see my 2018 installation is now defaulting to the historic repository
There are several ways that can be done and the easiest way which I have already told you is to use tlmgr-gui the other way is to use tlmgr direct and either set the default via the option command or change your command line slightly
tlmgr install koma-script --repository ftp://tug.org/historic/systems/texlive/2018/tlnet-final
