Drain the soaked chickpeas and pat them dry with a clean towel or paper towels.
Grate the onion into a bowl, then squeeze the pulp in a clean towel to remove as much liquid as possible. Discard the liquid.
In a food processor, pulse the chickpeas, squeezed onion, scallions, dill, mint, parsley, and garlic until finely ground but not pureed, like coarse sand. Scrape down the sides once or twice.
Transfer the mixture to a bowl. Add the flour, baking soda, salt, and pepper, and mix with your hands until it holds together when pressed. Add an extra tablespoon of flour if it still feels too wet to shape.
Cover and chill the mixture in the fridge for 20 minutes. This firms it up so the patties hold their shape in the hot oil.
Pour the olive oil into a 26 cm / 10-inch skillet to a depth of about 1.5 cm / half an inch. Heat over medium heat until it reaches 175C/350F, a small piece of dough should sizzle right away when dropped in.
Shape the chilled mixture into 40 g balls and flatten slightly into patties, about 20 in total.
Fry the patties in batches of 5 to 6, without crowding the pan, for 2 to 3 minutes per side until golden brown and crisp on both sides.
Transfer the fried fritters to a paper-towel-lined plate to drain briefly.
Serve warm with lemon wedges and a spoon of plain yogurt on the side.