Remove apt repository?

Solution 1:

The repositories are stored in a file located at /etc/apt/sources.list. You can edit that to suit your needs.

Simple. Some times you'll go to /etc/apt/sources.list and wont find the repository that's misbehaving.

Solution is to use -r like so..

Line below is what you ran to add the repository that probably is no longer available / valid (abc & def in this case are just placeholders)

sudo add-apt-repository ppa:abc/def

Remove it like so

sudo add-apt-repository -r ppa:abc/def

Now run sudo apt update again and all your problems should be gone!