Just whatever you do, stay away from Plaid, it prompts for login/password giving full access to one's online bank accounts for Zak George, its CEO and then according to his non-privacy policy he "shares" (such a nice word) your information with third parties, transaction history, loans, you name it. The screen uses bank logos to fool people into believing all they are doing is logging into their bank privately, with the rhetoric couched in all sorts of bromides of course, like "easy".
Companies that use Plaid prove they don't give a shi^ about your privacy or security. These are some of them:
Binance Blockfolio Coinbase Gemini Okcoin Robinhood (switched to it not so long ago)
Abra Bitflyer Bitso Bitstamp Blockfi Bybit Coinbench GiveBitcoin Newton Ontology Paxos River Voyager (VGX)

Might be possible to fake it out at some places by entering a bank name they can't find like First Bank of Smarter Sheep. Sometimes it will fall back to the ACH process of 2 small deposits and then you're all set.

Possibly others like Plaid also trying to copy them.

Aside from bank connection, there's credit card with high fees, which is what I encountered at kucoin. By the time I had bought BTC and transferred to ARRR via TradeOgre, it seems like I'd lost over 30%, but on this point I'm not certain as the process by kucoin was not direct about the fees. Many places show it in BTC ... have to do the math. I'm told buying USDT (Tether) or LTC first has lower fees than BTC.