Thanks for reporting this issue and making Ubuntu better. This seems to be a problem with either the file that provides the links to the repositories (sources.list) or some other files related to the upgrading process. This may have been caused by the manual installation you tried. If you have still this issue it could be convenient to convert this report to a question so that you can get support on how to solve it, otherwise please kindly ignore this message.
Thanks for reporting this issue and making Ubuntu better. This seems to be a problem with either the file that provides the links to the repositories (sources.list) or some other files related to the upgrading process. This may have been caused by the manual installation you tried. If you have still this issue it could be convenient to convert this report to a question so that you can get support on how to solve it, otherwise please kindly ignore this message.