Same here, once a month, but my previous parish now has 5 Deacons, so they don’t often don’t preach in a given month at all. But there is alway s 2 present at each Mass, even the Spanish Masses, where none of them speak Spanish at all.
We had a particularly awkward homily once given by a Deacon (disclaimer, I knew what he meant to say, he just said it awkwardly) and some of the parishioners jumped all over the pastor for allowing him to preach. He was off the rotation for the summer, but he’s back now and doing fine.
At my present parish, the 2 Deacons preach about once a month as well. They split themselves up between the various Masses. Father encourages it, and we get together as a staff every Thursday to offer homily suggestions based on the readings 2 weeks out.