Many thanks for the advice and for the video. I have already removed the bracket (or cassette, as is usually called here -Spain-). I did watch a number of instruction videos before and had, fortunately, figured out the reverse thread.
Regarding the impact wrench, given the original thread comments on the difficulty of removing the bracket, having to use a G clamp to press the socket into the nut, I thought it was worth sharing a tip that worked perfectly. In my case, I soon realized, after a couple of attempts, that the use of a long ratchet wrench was not going to work that well, the issue being, precisely, that, with such a long lever and the force applied at the end of the lever, the socket would slightly tilt, so that the splines in the socket would not fit perfectly in the grooves in the bracket. Exactly what the original thread and some other members in the forum were saying. Given that the risk of either ruining the socket or (much more important), the bracket, can only be minimized by ensuring that they both fit perfectly, and given that the best way to do that is to apply downwards pressure directly above the socket to push the splines as vertically as possible into the bracket nut grooves, I thought that the impact wrench, that allows the user to simply press down while the tool does the twisting force, was the best tool for the job. Sure enough, nuts went out easily at the first attempt, which had not been the case with the ratchet wrench. Needless to say, and given that electric impact wrenches allow to modulate the number of impacts and, in some cases, the torque, I started carefully, checking that there was a very slight movement with the first impacts and that the splines and grooves were not wearing, and continued when comfortable that it was working.