There is a good analysis of some of the immediate effects of Brexit on the art market, as attached. Of course, it is possible that things will settle down and we will all get used to filling out all the necessary new forms, but at the moment it feels like a huge added set of problems and burdens on top of COVID, not getting rid of red tape, but adding it:-

https://news.artnet.com/market/implications-of-brexit-1934921