You can cook pretty much anything in it. Poke around there are quite a few vegetable recipes, mushrooms are a popular option, and there’s likely to be specific vegan recipes floating around out there. Many of the big “wow” techniques are really only going to be relevant to meat. I’ve used it to par-cook potatoes before frying, or to poach vegetables before grilling. But the results aren’t necessarily any different than when I do the same thing the conventional way. Its just easier and more convenient, which is probably the biggest surprise I’ve had since getting the thing. Its a huge labor saver in a lot of cases even when you aren’t shooting for “only with sous vide” results. Especially when I’m cooking for 15+ people.
Not being a vegan or vegetarian I couldn’t really tell you about anything in that realm that would be analogous to all the meaty magic. As was mentioned in the OP something about the vacuum seal + low temperature thing seems to exaggerate certain flavorings. Especially herbs and aromatics. I’ve seen this exploited to give stronger flavors to tofu. Seal it up with some heavily flavored fat and steep it at low temp for a while before searing. I’m reasonably sure sous vide would be useless for beans, lentils, or grains of any sort unless pre-cooked. So depending on what you rely on for main dishes it might not be all that relevant for you.
