I'm on GNOME, go to Gnome Software, search for Okular, click Install - boom it's installed. Since it's made available via flathub.org, Okular and the shared KDE

I'm on GNOME, go to Gnome Software, search for Okular, click Install - boom it's installed. Since it's made available via flathub.org, Okular and the shared KDE platform libraries are installed as self-contained flatpaks. To ignorant me, looks and runs like any other application.