Can. 766
The laity may be allowed to preach in a church or oratory if in certain circumstances it is necessary, or in particular cases it would be advantageous, according to the provisions of the Episcopal Conference and without prejudice to can. 767 §1. Can. 767 §1 The most important form of preaching is the homily, which is part of the liturgy, and is reserved to a priest or deacon. In the course of the liturgical year, the mysteries of faith and the rules of Christian living are to be expounded in the homily from the sacred text.
So the only situations in which "lay preaching" can be permitted would be outside the context of the Mass.
In all the years of going to my chuch,it was only once we had a lay person speak. It was a time when volunteering was low and one of our trustees addressed the parish regarding the importance of the faith community to be active within the parish.
Of course we do have missionaries, some of whom are nuns (layperson) speak annualy.