After seeing the press articles about the Lineage 21 release, I was waiting for this question to come up. 
As you may be aware we are still in the process of releasing the next set of A13 upgrades.
While /e/OS has been forked from LOS it does not mean that we just copy the code and add our logo. There are changes in the code base which come with /e/OS. We will need to upgrade our code base, make the modifications and test it.
This process can take a couple of months at the least. I shall share the plans for A14 upgrade once the team gets down to it.