That’s not correct! Of course there is a package kicad-libraries, this is a metapackage that is depending on all libraries related to KiCad as described within the package description (if people would just read it).
Please distinguish between the official Ubuntu packages and other possible packages provided by PPAs! And by this how packages and the dependency resolver can act. The packages that are provided by rs-reynaud and Ubuntu doesn’t have always suitable values to solve package versions correctly every time. Doing this “right” is the hard thing in packaging software.
O.k. now looking at the issue.
Ubuntu 20.04 is the new LTS version of Ubuntu. Ubuntu is pulling most of it’s packages from Debian testing. The soure package site for KiCad in Ubuntu is here:
Looking at the binary package site for Focal Fossa (aka 20.04) you see the current provided versions for KiCad.
And these versions are equal to the version in Debian testing (except for the appendix build2), and also equal to the latest official release of KiCad, this is right now is 5.1.5. So you normally doesn’t need to enable the PPA from js-renaud as long you want to use the stable version. Seems to me people just blindly do c&p without really thinking about they doing.
This step is useless, as written above, kicad-libraries is a metapackage that is depending on all the packages you have installed previously. Currently you don’t need to do anything.
Even on Ubuntu with no added PPA from js-reynaud it’s enough to just call sudo apt install kicad. No need to use --no-install-recommends on a desktop system! The kicad binary package has a recommends on kicad-libraries and kicad-demos, the latter is a binary package which you requested to install, kicad-libraries itself has dependencies on kicad-footprints, kicad-symbols, kicad-templates and these are also the real binary packages you have requested to install.
$ apt show kicad
...
Recommends: kicad-libraries, kicad-demos, xsltproc
...
$ apt show kicad-libraries
...
Depends: kicad-footprints, kicad-symbols, kicad-templates
...
It’s extremely helpful to understand how the package system is working and how to read the various information you can get from it. PPAs can provide really a great user experience and enhance the core system of Ubuntu, but you need to know and understand how they are designed to work.
And please don’t touch anything in /var/{cache,lib}/apt if you not really know what you doing, this can damage your system completely!