`dbus-broker` is part of the Bus1 project and is slated to replace the reference implementation of `dbus-daemon` in a number of distributions by the next distribution release cycle (eg, Fedora 29). `dbus-broker` aims to be a conforming implementation of the DBus standard, but drops everything marked DEPRECATED in the standard and a few other features not explicitly part of the standard. More details here: https://github.com/bus1/dbus-broker/wiki/Deviations
One known change that affects KDE Connect is deprecation of "eavesdropping" via `org.freedesktop.DBus.AddMatch()` in favour of `org.freedesktop.DBus.Monitoring.BecomeMonitor()`. This is a relatively easy fix, but has some differing requirements to `AddMatch()`. `BecomeMonitor()` must be called on a dedicated DBus connection, and the exported interface method `Notify()` (used to eavesdrop and proxy libnotify notifications) must be exported on that connection. The match string itself can stay the same, but exclude the `eavesdrop=true` parameter.
More information here: https://dbus.freedesktop.org/doc/dbus-specification.html#bus-messages-become-monitor