It's a session D-Bus service, defined in file
/usr/share/dbus-1/services/org.kde.kaccessible.service. It is started indirectly by
systemd's user session manager.
systemctl --user status.
When a GUI desktop session begins, one of the user-level services started at that time is the accessibility bus service:
at-spi-dbus-bus.service. It starts
at-spi-bus-launcher, which in turn starts an instance of
dbus-daemon for the accessibility bus, and the actual D-Bus services of the accessibility bus, including
In order to disable just the
kaccessibleapp service, as far as I can see, the file
/usr/share/dbus-1/services/org.kde.kaccessible.service would need to stop existing in that directory; there does not seem to be any other way to control the start-up of that service specifically.
If you want to disable the entire accessibility bus, run
systemctl --user stop at-spi-dbus-bus.service as your regular user account, then verify nothing important to you is broken by that. If something is wrong, just logging out and back in restarts the accessibility bus again. To persistently disable the accessibility bus from starting, run
systemctl --user disable at-spi-dbus-bus.service. To undo, replace
If some other session-level service requires the accessibility bus in its
systemd configuration, the accessibility bus service may still get started to fulfill that requirement. To explicitly forbid the start of the accessibility bus even if something else requires it, run
systemctl --user mask at-spi-dbus-bus.service. To undo, replace