Something similar was posted in the "Ideas" forum, but I thought I would post over here in "Problems."
I'm using version 126.96.36.199192. The service outline for Matins shows an option for "Antiphon (Common)" or "Antiphon (Lectionary)" for the Venite. When you select "Antiphon (Lectionary)" if your preference is set for the Three Year Lectionary, you get the little yellow warning triangle that says there is no content for that element.
There is a workaround for Advent. If you search for "Antiphon" in the search box, there are lectionary antiphons for Advent 1, 2, and 3 under the One Year lectionary.
I have not been able to find the Lenten antiphon.