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