I've updated all packages in kde-*.scm files (may have missed something),
plus some KDE games in games.scm. I was hesitant about sending 235 patches
so I just attached them as a zip, and pushed the branch to my notabug 
(subject to rebasing):

https://notabug.org/Brendan/guix/src/wip-kde-updates-21.08

I used refresh -l to find all dependent packages and basically
everything build apart from some packages like openstack that are
already broken.

Since there are a lot of patches, it's probably I forgot something
important or left something incomplete.

In the grantleetheme package, there was a large C++ I deleted. I'm not
really sure if any patching is still need since it looks complicated

Other packages with changes to patches include
kdbusaddons, kpackage, kplasma-framework, grantleetheme, kmail.

* Reproducibility bugs
- The packages kparts, ktexteditor, plasma-framework, krunner, kio produce
.bz2 files in /share/kdevappwizard/templates/ that include timestamps on
the directories. Any ideas how to fix that?

- kdevelop looks even nastier, containing entire mime/application .xml
files in one build that weren't present in the previous.
- kdelibs4support produces .so's with symbols in varying order.
- sonnet: .so differences (already present in current guix version)

Package list:

akonadi akonadi-calendar akonadi-contacts akonadi-mime akonadi-notes akonadi-search akregator ark attica audiocd-kio baloo baloo-widgets bluez-qt bomber bovo breeze breeze-icons dolphin dolphin-plugins dragon elisa extra-cmake-modules ffmpegthumbs granatier grantleetheme juk k3b kactivities kactivities-stats kaddressbook kajongg kalarmcal kamoso kapidox kapman karchive kate kauth kblackbox kblocks kbookmarks kbounce kbreakout kcachegrind kcalendarcore kcalendarsupport kcalutils kcmutils kcodecs kcompletion kconfig kconfigwidgets kcontacts kcoreaddons kcrash kdav kdbusaddons kdeclarative kdeconnect kdecoration kded kde-frameworkintegration kdegraphics-mobipocket kdelibs4support kdepim-runtime kdesignerplugin kdesu kdevelop kdewebkit kdf kdiagram kdiamond kdnssd kdoctools kemoticons keventviews kfilemetadata kfourinline kget kglobalaccel kgoldrunner kgpg kguiaddons khelpcenter kholidays khtml ki18n kiconthemes kidentitymanagement kidletime kigo killbots kimageformats kimap kincidenceed
 itor kinit kio kirigami kiriki kitemmodels kitemviews kjobwidgets kjs kjsembed kjumpingcube kldap kleopatra klines kmag kmahjongg kmail kmailcommon kmailimporter kmailtransport kmbox kmediaplayer kmessagelib kmime kmines kmix kmousetool kmouth knavalbattle knetwalk knewstuff knotes knotifications knotifyconfig kolf kollision konquest konsole kontactinterface konversation kopete korganizer kpackage kparts kpeople kpimcommon kpimtextedit kplotting kpmcore kpty kqtquickcharts krdc kreversi krfb krita kross krunner kscreenlocker kservice kshisen ksirk ksmtp ksnakeduel kspaceduel ksquares ksshaskpass ksudoku ksyntaxhighlighting ksystemlog ktexteditor ktextwidgets ktnef ktorrent ktouch ktuberling kubrick kunitconversion kwallet kwave kwayland kwidgetsaddons kwindowsystem kxmlgui kxmlrpcclient libgravatar libkcddb libkcompactdisc libkdegames libkdepim libkexiv2 libkgapi libkleo libkmahjongg libkomparediff2 libkscreen libksieve libksysguard libktorrent lskat modemmanager-qt networkmanager-q
 t okteta okular oxygen-icons palapeli picmi plasma-framework poxml prison pulseaudio-qt purpose qca qqc2-desktop-style smb4k solid sonnet sweeper syndication threadweaver yakuake zeroconf-ioslave