[jkgung]

With using a nightly build repository it works - returning back to the stable repository I have the problems described in the first post.
Output of apt policy kodi kodi-pvr-mediaportal-tvserver:

kodi:
  Installed: 2:17.6+git20180430.1623-final-0bionic
  Candidate: 2:17.6+git20180430.1623-final-0bionic
  Version table:
 *** 2:17.6+git20180430.1623-final-0bionic 500
        500 http://ppa.launchpad.net/team-xbmc/ppa/ubuntu bionic/main amd64 Packages
        500 http://ppa.launchpad.net/team-xbmc/ppa/ubuntu bionic/main i386 Packages
        100 /var/lib/dpkg/status
     2:17.6+dfsg1-1ubuntu1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
kodi-pvr-mediaportal-tvserver:
  Installed: (none)
  Candidate: 2.4.14+dfsg1-1build2
  Version table:
     2.4.14+dfsg1-1build2 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages