Ubuntu 16.04 could not be upgraded to 18.04 due to ppa conflict. I have submitted the this issue. The comment about this bug is not sufficient to solve this issue, simply, because I could not able to determine which ppa(s) responsible to this issue.
I also unchecked all ppa(s) like the following screen shot
Is there any suggested solution that allows me to upgrade 16.04 to 18.04?
