I have downloaded the mod and completed the research requirement. I now have a fine looking machine gun equipped ironclad gunboat which is otherwise similar to Earendel's ironclad, which I also have.

While the land-turret mortar and the chemical and fire mortar rounds now appear in the Research section to be associated with the Earendel ironclad, I cannot find where they are available for crafting.

So, unless I'm missing something, this mod only provides a machine gun ironclad variant. The land-turret does not actually exist, nor do the special mortar rounds.