Oniony Brothy Beans

Name: Oniony Brothy Beans
Ingredients: 2 Tbsp. extra-virgin olive oil or vegetable oil; 2 large white onions, cut through root ends into 1-thick wedges; 1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt, plus more; 5 garlic cloves, thinly sliced; 1 tsp. freshly ground black pepper; 1½ tsp. thyme leaves, plus more for serving; 4 cups low-sodium vegetable broth; ¾ cup seasoned rice vinegar; 2 15-oz. cans cannellini (white kidney) beans, rinsed; 8 oz. frozen white pearl onions (about 1½ cups); 1 Tbsp. distilled white vinegar; Slices of crusty country-style bread, toasted (for serving)