I purged all traces of previous versions of texlive after doing the upgrade to 18.04, but I cannot now install texlive, texlive-full, or texlive-xetex.
For example, sudo apt install texlive gives me the message:
Package texlive is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'texlive' has no installation candidate
Likewise sudo apt-cache policy texlive gives me
texlive
Installed: (none)
Candidate: (none)
Version table:
I can install texlive-base, but I need texlive-xetex