Flag things being incorrectly closed.
Let us sort them out. That's the short answer.
The longer extension to that is to [please] just be careful what you're looking at.
https://askubuntu.com/questions/1161907/problem-when-i-try-update-linux-ubuntu-18-10 is about apt-get update errors. It is off-topic. You're right, the actual problem here is [probably] that ...
Ubuntu is one of the most popular Linux distribution over the world. So there may be some general questions relevant to any Debian based Linux distro. But that does not mean he/she can't post it here. Because if it is a general question for Debian based distro there will be a 90% probability that ubuntu also have the same question.