Personally I just got a 3pt trencher. 3' deep & 6" wide. Got a killer deal on it & have several projects for it myself & so do a few friends. Will likely get sold after that. I know a lot of others put basically an elbow on the back of a subsoiler & use that, basically the same thing as the agri-supply link earlier.
Be very careful about burying Ethernet. You can get ground loop issues between different buildings. Commercially people never run copper, they only run fiber between buildings because of this. I did run conduit & put Ethernet in it out to my chicken coop & up to my shop when we did a different trenching project. I'm a huge believer in putting in conduit rather than wire of any sort. That way you can replace, repair or upgrade it as needed without having to trench again. Some areas have huge issues with critters eating small cable that gets buried.