SUMMARY
Crash happens everytime I apply new configuration. It doesn't matter what kind of settings I change.

STEPS TO REPRODUCE
1. Change configuration in systemsettings
2. Click on apply
3. Crash

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 33
(available in About System)
KDE Plasma Version: 5.20.90
KDE Frameworks Version: 5.78
Qt Version: 5.15.2


Backtrace:
[KCrash Handler]
#4  0x00007f4149069034 in QWaylandClientExtensionPrivate::handleRegistryGlobal (data=0x564ef81115c0, registry=0x564ef6566570, id=76, interface=..., version=1) at global/qwaylandclientextension.cpp:67
#5  0x00007f41490553b1 in QtWaylandClient::QWaylandDisplay::registry_global (this=<optimized out>, id=<optimized out>, interface=..., version=<optimized out>) at qwaylanddisplay.cpp:396
#6  0x00007f4149071b53 in QtWayland::wl_registry::handle_global (data=0x564ef65623e0, object=<optimized out>, name=76, interface=0x564ef8da2f10 "org_kde_kwin_blur_manager", version=1) at qwayland-wayland.cpp:94
#7  0x00007f4146a83b10 in ffi_call_unix64 () from /lib64/libffi.so.6
#8  0x00007f4146a830a3 in ffi_call () from /lib64/libffi.so.6
#9  0x00007f4148fc38fe in wl_closure_invoke.constprop () from /lib64/libwayland-client.so.0
#10 0x00007f4148fc3fcb in dispatch_event.isra () from /lib64/libwayland-client.so.0
#11 0x00007f4148fc419c in wl_display_dispatch_queue_pending () from /lib64/libwayland-client.so.0
#12 0x00007f414904e0d3 in QtWaylandClient::QWaylandDisplay::flushRequests (this=0x564ef65623d0) at qwaylanddisplay.cpp:221
#13 0x00007f414b3d23c0 in doActivate<false> (sender=0x564ef65898f0, signal_index=3, argv=0x7ffcc2d3e640) at kernel/qobject.cpp:3898
#14 0x00007f414b3d577a in QSocketNotifier::activated (this=this@entry=0x564ef65898f0, _t1=..., _t2=<optimized out>, _t3=...) at .moc/moc_qsocketnotifier.cpp:178
#15 0x00007f414b3d5f21 in QSocketNotifier::event (this=0x564ef65898f0, e=0x7ffcc2d3e760) at kernel/qsocketnotifier.cpp:302
#16 0x00007f414bf30ec3 in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x564ef65898f0, e=0x7ffcc2d3e760) at kernel/qapplication.cpp:3632
#17 0x00007f414b3a2bd8 in QCoreApplication::notifyInternal2 (receiver=0x564ef65898f0, event=0x7ffcc2d3e760) at kernel/qcoreapplication.cpp:1063
#18 0x00007f414b3f0157 in socketNotifierSourceDispatch (source=0x564ef65a3f50) at kernel/qeventdispatcher_glib.cpp:107
#19 0x00007f414916696f in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
#20 0x00007f41491b8758 in g_main_context_iterate.constprop () from /lib64/libglib-2.0.so.0
#21 0x00007f4149163d43 in g_main_context_iteration () from /lib64/libglib-2.0.so.0
#22 0x00007f414b3ef6f3 in QEventDispatcherGlib::processEvents (this=0x564ef6589710, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#23 0x00007f414b3a157b in QEventLoop::exec (this=0x7ffcc2d3e970, flags=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:69
#24 0x00007f414b3a91b4 in QCoreApplication::exec () at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#25 0x0000564ef465dd3b in main (argc=<optimized out>, argv=0x7ffcc2d3ea90) at /usr/src/debug/plasma-systemsettings-5.20.90-1.fc33.x86_64/app/main.cpp:221
[Inferior 1 (process 15013) detached]