Drain and rinse the chickpeas and place them in a large mixing bowl.
Trim and thinly slice the spring onions and add them to the bowl.
Dice the red pepper and add to the chickpeas.
Halve the cucumber lengthways, scoop out the seeds with a spoon, then roughly chop the flesh and add it to the bowl.
Finely chop the parsley and/or mint and add to the salad.
In a small jug or bowl, whisk together the lemon juice, olive oil, sumac, salt, and pepper. Add the minced garlic and dried mint if using.
Pour the dressing over the salad and toss well to combine.
Let the salad rest for about 10 minutes before serving to allow the flavours to develop.