Different aggregators will have different connections established based on relationships and also the priority of the bank. I've seen a ton of different options based on the fintechs apps I use from Plaid, MX, Finicity, etc. Long story short, it's usually the big banks. Different aggregators have different priorities around the amount of traffic they send over these connections though. Candidly I don't know why that is, but I have some hypotheses. Ultimately though you can assume all of the above names will have accounts like Chase, Wells, Citi, Cap One, BOA, US Bank etc.