See also: https://www.freedesktop.org/software/PackageKit/pk-faq.html#session-methods gnome-software and apper (unmaintained) has support for this, would be nice if discover (maintained) could grow support as well.
Makes sense, maybe it would be best if we split PkSession out of apper and maintain it rather than introducing this in Discover UI. What do you think? I don't have experience with that interface and I'm not sure where it's used. It looks dated either way, as it doesn't support AppStream anyway...
Since Apper is sort of ported to kf5 (never tested it myself), an option could be to put a build flag to only build the session interface. Sadly I can't deal with this ATM (I may try compiling it to check the state).
Daniel, see also bug #375347 for a current fatal error trying to use apper-pk-session
Just created a review request at https://phabricator.kde.org/D5194 which implements the ability to optionally disable parts of Apper's selection of tools, as Daniel suggests in comment 2.