Currently there is LyX 2.2.3-5 in Ubuntu 18.04 LTS (Bionic).
There is discussion in https://bugs.launchpad.net/ubuntu/+source/lyx/+bug/1595358 about getting 2.1.5 into 16.04 LTS (Xenial) and they claim 2.1.5 can read and write the file format of 2.2.x. If you have concerns about 2.1.5 not being enough, please leave a comment in that bug.
Currently there is LyX 2.2.3-5 in Ubuntu 18.04 LTS (Bionic).
There is discussion in https:/ /bugs.launchpad .net/ubuntu/ +source/ lyx/+bug/ 1595358 about getting 2.1.5 into 16.04 LTS (Xenial) and they claim 2.1.5 can read and write the file format of 2.2.x. If you have concerns about 2.1.5 not being enough, please leave a comment in that bug.
So perhaps this bug can be closed?