The times are fixed with only two options. I don't know what might change the 'as a rule' part. Don't forget that CET is one hour ahead of us so either 18:00 or 20:05. I expect TV all dominate, as usual.
Article 22 Venues and kick-off times
22.01 As a rule, matches in the UEFA Europa League kick off at 19.00CET or 21.05CET. The UEFA administration sets the kick-off times on the basis of the draw. Exceptions to this rule can be made by the UEFA administration.