flatpak install flathub org.kde.Platform//5.15-22.08
This sample command would install the KDE Platform Runtime. But how do I check what's inside of it? E.g. what binaries or libraries it contains (possibly after installation).
Runtimes are stored in these locations (system and user installations accordingly):
/var/lib/flatpak/runtime/
.local/share/flatpak/runtime/
For example the runtime files in question would be located here:
/var/lib/flatpak/runtime/org.kde.Platform/x86_64/5.15-22.08/active/files