Preheat the broiler to high and position a rack 5 to 6 inches from the heat source. On a cutting board, mash the garlic with the side of your knife, adding a little salt as you work and using the heel of your hand to apply pressure, until the garlic turns into a paste. Place the paste in a medium bowl and combine with the lemon juice and zest and the thyme. Whisk in the EVOO. Add the tuna and flake it with a fork, mixing it with the dressing. Add the artichokes along with the onion, celery and arugula. Toss the salad to combine and season with salt and lots of pepper.
Place the English muffins on a rimmed baking sheet and toast under the broiler. When golden, remove the baking sheet and top each half with a slice of tomato. Using an ice cream scoop, make a mound of the tuna and pile 1 mound on top of each of the 8 tomato slices. Top the tuna with a slice of provolone cheese and return the sammies to the oven to melt the cheese.