I was unaware in the beginning that Ubuntu is not completely free software, as it uses non-free components.
Is it possible to overcome the system's dependence on these (such as replacing Linux kernel by linux-libre) and make my current installation of Ubuntu 16.04 completely free software (assuming I do not make any non-free additions voluntarily)?
mainanduniversesections is libre. It'srestrictedandmultiversethat contain non-free software. So, remove anything installed from those sections of the repository. – muru Feb 02 '17 at 09:03