Ubuntu sudo apt get update 404 Not Found problem

Most of the repositories and PPAs in your sources.list are no longer available and are throwing errors. I'd recommend restoring the default repositories.

1. First, restore the default focal repositories using these commands:

   mkdir ~/solution
   cd ~/solution/
   wget https://gist.githubusercontent.com/ishad0w/788555191c7037e249a439542c53e170/raw/3822ba49241e6fd851ca1c1cbcc4d7e87382f484/sources.list
   sudo rm -r /etc/apt/sources.list
   sudo cp -r ~/solution/sources.list /etc/apt/sources.list
   

2. Remove all the PPAs in your system:

   sudo mv /etc/apt/sources.list.d/* ~/solution
   

3. Update the repositories:

   sudo apt update
   

Now there should be no errors.
Good Luck!