SUMMARY
I have kdeconnectd crashing a few times a day. As far as I'm aware it is not in response to anything I specifically do, but Android events that are relevant to kdeconnect happen all the time, so...

I'm running Neon unstable fully up to date.

Here is the relevant crash report:

Thread 1 (Thread 0x7f91324fe800 (LWP 3819630)):
[KCrash Handler]
#4  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#5  0x00007f9135a62859 in __GI_abort () at abort.c:79
#6  0x00007f9134e5eed2 in _dbus_abort () at ../../../dbus/dbus-sysdeps.c:93
#7  0x00007f9134e81570 in _dbus_warn_check_failed (format=format@entry=0x7f9134e91dc8 "arguments to %s() were incorrect, assertion \"%s\" failed in file %s line %d.\nThis is normally a bug in some application using the D-Bus library.\n") at ../../../dbus/dbus-internals.c:281
#8  0x00007f9134e81cde in _dbus_warn_return_if_fail (function=function@entry=0x7f9134e906d0 <__func__.5446> "dbus_message_iter_append_basic", assertion=assertion@entry=0x7f9134e8fffe "*bool_p == 0 || *bool_p == 1", file=file@entry=0x7f9134e8ff3d "../../../dbus/dbus-message.c", line=line@entry=2777) at ../../../dbus/dbus-internals.c:936
#9  0x00007f9134e726a9 in dbus_message_iter_append_basic (value=0x7ffdd9f04300, type=98, iter=0x7ffdd9f04440) at ../../../dbus/dbus-message.c:2777
#10 dbus_message_iter_append_basic (iter=iter@entry=0x7ffdd9f04440, type=type@entry=98, value=value@entry=0x7ffdd9f04300) at ../../../dbus/dbus-message.c:2732
#11 0x00007f91364191b3 in q_dbus_message_iter_append_basic (value=0x7ffdd9f04300, type=98, iter=0x7ffdd9f04440) at qdbus_symbols_p.h:336
#12 qIterAppend (arg=0x7ffdd9f04300, type=98, ba=<optimized out>, it=0x7ffdd9f04440) at qdbusmarshaller.cpp:54
#13 QDBusMarshaller::append (arg=<optimized out>, this=0x7ffdd9f04420) at qdbusmarshaller.cpp:79
#14 QDBusMarshaller::appendVariantInternal (this=0x7ffdd9f04420, arg=...) at qdbusmarshaller.cpp:438
#15 0x00007f913641a9c6 in QDBusMarshaller::append (this=this@entry=0x7ffdd9f04660, arg=...) at qdbusmarshaller.cpp:221
#16 0x00007f91364189b0 in QDBusMarshaller::appendVariantInternal (this=this@entry=0x7ffdd9f04660, arg=...) at ../../include/QtDBus/../../src/dbus/qdbusextratypes.h:164
#17 0x00007f91363e2c2f in QDBusMessagePrivate::toDBusMessage (message=..., capabilities=..., error=error@entry=0x7ffdd9f04800) at ../../include/QtCore/../../src/corelib/tools/qlist.h:313
#18 0x00007f91363d0fa8 in QDBusConnectionPrivate::send (this=0x7f9124003a00, message=...) at qdbusintegrator.cpp:1931
#19 0x00007f91363d5de0 in QDBusConnectionPrivate::activateInternalFilters (this=this@entry=0x7f9124003a00, node=..., msg=...) at qdbusintegrator.cpp:1423
#20 0x00007f91363dbd87 in QDBusConnectionPrivate::activateObject (pathStartPos=<optimized out>, msg=..., node=..., this=0x7f9124003a00) at qdbusintegrator.cpp:1495
#21 QDBusConnectionPrivate::activateObject (this=0x7f9124003a00, node=..., msg=..., pathStartPos=<optimized out>) at qdbusintegrator.cpp:1436
#22 0x00007f91363def6c in QDBusActivateObjectEvent::placeMetaCall (this=0x7f91240ca830) at qdbusintegrator.cpp:1606
#23 0x00007f91360f0129 in QObject::event (this=0x5585114b8cc0, e=0x7f91240ca830) at kernel/qobject.cpp:1314
#24 0x00007f9136c98cc3 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#25 0x00007f9136ca1c70 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#26 0x00007f91360c26aa in QCoreApplication::notifyInternal2 (receiver=0x5585114b8cc0, event=0x7f91240ca830) at ../../include/QtCore/5.15.0/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:325
#27 0x00007f91360c4fa1 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x558510f3aa60) at kernel/qcoreapplication.cpp:1815
#28 0x00007f913611d837 in postEventSourceDispatch (s=0x558511063450) at kernel/qeventdispatcher_glib.cpp:277
#29 0x00007f9134748fbd in g_main_dispatch (context=0x7f912c005000) at ../../../glib/gmain.c:3309
#30 g_main_context_dispatch (context=context@entry=0x7f912c005000) at ../../../glib/gmain.c:3974
#31 0x00007f9134749240 in g_main_context_iterate (context=context@entry=0x7f912c005000, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../../../glib/gmain.c:4047
#32 0x00007f91347492e3 in g_main_context_iteration (context=0x7f912c005000, may_block=may_block@entry=1) at ../../../glib/gmain.c:4108
#33 0x00007f913611ce92 in QEventDispatcherGlib::processEvents (this=0x55851106b290, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#34 0x00007f91360c11bb in QEventLoop::exec (this=this@entry=0x7ffdd9f04f60, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#35 0x00007f91360c9354 in QCoreApplication::exec () at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#36 0x0000558510233eb8 in ?? ()
#37 0x00007f9135a640b3 in __libc_start_main (main=0x558510233a40, argc=1, argv=0x7ffdd9f051b8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffdd9f051a8) at ../csu/libc-start.c:308
#38 0x000055851023418e in _start ()
[Inferior 1 (process 3819630) detached]

It looks to be related qdbus and possibly has something to do with bug #412665 and bug #425607