* Upgrading from LyX 2.1.x:
-With LuaTeX, LyX now uses polyglossia instead of babel if the language
-package option "Automatic" is selected. In order to use babel, select
-"Always babel" instead.
-
The format of preference and session files has changed. LyX 2.2.x is able to
read old files but will save them in the new format.