Elementary os 6 can't sudo apt-get update or any other apt-get

Question

It returns the following after $ sudo apt update or $ sudo apt-get update or etc...

Err:12 http://ppa.launchpad.net/mpstark/elementary-tweaks-daily/ubuntu focal Release 
  404  Not Found [IP: 91.189.95.85 80]\
Err:13 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xanial Release\
  404  Not Found [IP: 91.189.95.85 80]\
Reading package lists... Done                      
E: The repository 'http://ppa.launchpad.net/mpstark/elementary-tweaks-daily/ubuntu focal Release' does not have a Release file.\
N: Updating from such a repository can't be done securely, and is therefore disabled by default.\
N: See apt-secure(8) manpage for repository creation and user configuration details.\
E: The repository 'http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xanial Release' does not have a Release file.\
N: Updating from such a repository can't be done securely, and is therefore disabled by default.\
N: See apt-secure(8) manpage for repository creation and user configuration details.

Answer 1

To remove the two PPAs that are giving you errors, you will need to edit your sources.list file.

Here's how:

0. Open Terminal (if it's not already open)
1. Edit the sources.list file:

   sudo vi /etc/apt/sources.list
   

   ^{Note: Feel free to use any text editor that you prefer. It does not need to be vi.}
2. Find the lines that refer to the URLs that are failing
3. Add a # to the start of the line, or remove the line completely
4. Update apt:

   sudo apt update 
   

You should not see the error(s) anymore.

If the URLs were not in sources.list, then they will be in a .list file somewhere inside the /etc/apt/sources.list.d directory. This really depends on how you added the PPAs to your system to begin with. However, the instructions above apply here as well. Open the file and comment out (or remove) the line.