I generally don't do it, because I'm not that organized, but I have done so in advance of my Saturday at the soup kitchen. Don't do potatoes, obviously, but I will certainly do onions, pepper, carrots, even meat if I have access to it; usually the meat is at the church, so generally not unless it's a pre-cook (I've done two or three Instant Pots of chuck roast, for instance, and then shredded it, though).
Stuff like squash, eggplant, etc., is easy enough to prep I don't bother with advance. But any hard veggies may get done a day or two in advance, and refrigerated.
We did something, I forget what, that called for caramelized onions, so I did those at home in the slow cooker well in advance.
