According to man sources.list the main paragraph underTHE DEB AND DEB-SRC TYPES: GENERAL FORMAT and some examples in it says
As an example, the sources for your distribution could look like this in one-line-style
deb http://us.archive.ubuntu.com/ubuntu xenial main restricted
deb http://security.ubuntu.com/ubuntu xenial-...
The sources you now use have different 'hash' data (a value calculated to show if there's corruption in file sources) so one or more of your packages on one of your sources disagrees with that package on another source. Solve it by changing sources in /etc/apt/sources.list, following the article at https://help.ubuntu.com/community/Repositories/Ubuntu .
Ubuntu Kernel Update Utility (UKUU) has now moved to a paid licensing model and is no longer available free in the Ubuntu Software Centre with the latest release for Ubuntu v19.
The cost of a personal license is $11.
If you want to install a kernel newer than the one available in Ubuntu for reasons like some new important feature, better hardware support, ...