This. I do this with mead often. We have a local raspberry farm and we like to pick them fresh, wash real good (make sure no stems and leaves or bugs) smash them a little bit and freeze them. Thaw a few hours before use. Berries have lots of nutrients. Yeast go nuts, if you have some sugars left in the wort combined with the sugar and nutrients in the raspberries, expect a good uptick in bubbling in the airlock/bubbler for at least part of the day.
Be sure to give the fermenter a little shake here and there (nothing major) to keep the fruit from ‘capping’ if allowed to sit for too long, it will begin to crust and even get moldy. If you keep it loose and wet (with alcohol from the wort/beer) it will be fine. It will start to sink after about a week (don’t quote me on that for beer, only used fruit in mead).
