kdbus
kdbus is an alternative in-kernel implementation of D-Bus.
Installation
Install the kdbusAUR package, then add kdbus=1 to the kernel parameters.
After rebooting, you can verify a working kdbus installation with:
$ journalctl -b | grep kdbus
kernel: kdbus: initialized systemd[1]: Inserted module 'kdbus'
Also check that /sys/fs/kdbus/ contains the 0-system/ folder, denoting the system bus. Another sign of a working kdbus installation is that, after invoking busctl, the DESCRIPTION column should not be entirely empty for all services.