For just changing a flat tire on my rv trailers and other non rv trailers I use my old 12T Truckers Special shorty hyd jack under the axle next to the you bolt. The jack came with a axle tube cradle adapter. Just a few strokes and the tire is off the ground enough to remove the flat and install the spare. Its jacked fully loaded and empty trailers with 1750 lb axles up to 12k axles.
The jack is old and is on its 3rd repack since the '70s era.
Now if your asking about jacking the trailer with all the wheels off the ground then I use a couple of floor jacks and lots of cribbing under the trailer frame rails front to back.