Too get a later version than 2.1.2, you would probably need to build Audacity from source, and you would have to upgrade gcc from 4.8 to 4.9 before you start.
(see: https://forum.audacityteam.org/t/building-audacity-2-1-2-on-ubuntu-14-04-lts/40691/1)
If you do want to do that, I would recommend building Audacity 2.2.1 rather than 2.2.0, (mostly because of the bug fixes in 2.2.1).
The source code for 2.2.1 is due to be released in a week or so, but it is likely to be the same as the current “2.2.1 RC1” which you can get here: https://www.fosshub.com/Audacity-devel.html ( audacity-minsrc-2.2.1-rc1.tar.xz - 9.84 MB | version: 2.2.1-rc1)