The INSTALL file was updated; for example KDE Plasma 5 is not required to run Krusader, as it's written in
https://docs.kde.org/trunk5/en/extragear-utils/krusader/faq.html#idm45666073100176 https://docs.kde.org/trunk5/en/extragear-utils/krusader/installation.html
Added some steps to follow if Krusader is already installed.