Adapted from https://paleoglutenfreeguy.com/grilled-italian-platter/
Prepare your gas grill, charcoal grill or grill pan over medium heat.
Add the balsamic vinegar to a small saucepan and place over medium heat (on the grill or stovetop). Simmer until reduced and thick and syrupy, about 15-20 minutes.
Trim the ends of the zucchini. Slice in half lengthwise. If very thick, slice into thirds lengthwise.
Trim the root end of the radicchio and romaine by thinly slicing off the very end of the root. You want the leaves to remain attached. If any outer leaves fall off, that's okay. Just discard or serve separately.
Lay the veggies on a large baking sheet, brush with half the avocado oil and sprinkle with salt. Flip over and brush with more avocado oil and sprinkle with salt. For veggies that have 3 sides (like the wedges of radicchio), brush the 3rd side with avocado oil and sprinkle with salt.
Add the veggies & sausages to the grill. Cook them, covered if using a gas or charcoal grill: - sausages: 8-10 minutes per side, or until an instant thermometer reads 145 degrees. Cook zucchini 5-6 minutes per side, radicchio & romaine 4-5 minutes per side, cut sides only
Arrange on a platter. Scatter the pistachios, dried cherries, olives and basil on top. Sprinkle with flaky sea salt and freshly ground black pepper. Serve with the balsamic syrup on the side, along with any cheese, if desired.