Aquafaba ("the cooking liquid of beans and other legumes like chickpeas") has intrigued me since I first heard about it. How much protein does it have?
Very little. According to the ESHA database, via https://cronometer.com/, 100g of aquafaba contains 1g of protein:
If you're interested in making meringues or something with aquafaba, go ahead and enjoy them. They're not meant to be a source of nutrition. You can get your protein elsewhere.