This change
https://fedoraproject.org/wiki/Changes/EnableTrimOnDmCrypt
has been slipped from F26 to F27. In the meantime, and for current
users, a magazine article how to turn this on by yourself seems like a
good idea.
sgallagh suggests
https://blog.christophersmart.com/2016/05/12/trim-on-lvm-on-luks-on-ssd-r...
as a resource
--
Matthew Miller
<mattdm(a)fedoraproject.org>
Fedora Project Leader