I bought a 5 pound second cut brisket today but got lazy and decided to experiment. I lathered it up in mustard and applied a generous amount of big bad beef rub. This is the same prep I do for smoking. I put a rack in my instant pot, a little beef broth and a drop of liquid smoke on the bottom. I cooked it for 90 minutes at high pressure with a natural release. I then put it in the oven for a few minutes to dehydrate the bark. Holy cow was that good. Incredibly tender and flavorful.
A couple of tweaks I would make next time. First, I would add a little more liquid smoke. The smoke flavor I got was good but subtle. Second, I would lose the fat cap completely. No need when cooking with a pressure cooker. Third, I would cook it for a little less. The meat was one step before fall apart. I like my brisket with a little more chew.