supa you are correct, the latest LTS version is still 13.
If you would like to try there is an asterisk13 version in the beta repository, but I'd only use it for testing purposes at this time, a new version is coming soon with some major changes to ensure the upgrade path.
Along with it, there si also an updated version of Dahdi (updated to 2.11) which is necessary for the update due to the requirements on the old dahdi package.
This version of Asterisk 13 comes bundled with PJSIP so it is supported.
Lastly, and I cannot stress this enough, this Asterisk13 version is for testing only and its not intended for production.
Let us know how your tests go!