v2.2.0 seems stable and is recommended by the author to update.

Many exciting and useful changes.

https://github.com/CISOfy/lynis/blob/master/CHANGELOG

From the Cisofy website:

= Lynis 2.2.0 (2016-03-18) =

We are proud to present this new release of Lynis. It is a major upgrade, and the
result of many months of work. This version includes new features and tests, and
many small enhancements. We encourage all to test and upgrade to this latest
release.

• Highlights

  The biggest change in this release is the optimization of several functions. It
  allows for better detection, and dealing with the quirks, of every single
  operating system. Some functions were fortified to handle unexcepted results
  better, like missing a particular binary, or not returning the hostname.

This release also enables tests to be shorter, by adding new functions. Some
functions were renamed or slightly changed, to provide more value to the tooling.
Another big change in this release is a wide set of optimizations and quality
testing. Outdated pieces were removed, or rewritten, to support features seen in
newer distributions.

In the area of compliance, adjustments have been made to start supporting more
in-depth testing for this. Ideal for companies who have a particular compliance
need, or want to test and enforce the system hardening levels of their systems.

Last but not least, many small changes make this software easier to use. On
our website we added new guides to provide help and support.

We like to thank our contributors, in particular Kamil Boratyński, Steve Bosek,
and Eric Light. Their contributions helped us greatly shaping this release.

Any interest?

Saw that you guys are going to publicly demo Kali soon. New release has moved up the priority ladder.

If it's feasible, upgrading lynis to the most recent version (which revamps some major things) would help to tidy up and modernize Kali for the best presentation.

Just a thought.

I have copied lynis 2.3.1 from Debian unstable into Kali Dev. It will appear shortly in Kali Rolling.