Having just read the latest Ethical Consumer report on current accounts, United Diversity are going to be switching from Santander (we opened the account when they were still Abbey National building society) to Starling Bank.
As you can see from the table above Triodos are the most ethical. But they charge for everything and don’t do debit cards (if I remember correctly).
Cumberland Building Society are the next best, but you can only open an account with them is you’re in Cumbria or South-West Scotland.
Starling Bank are rated joint 3rd place along with Nationwide and Monzo.
But Nationwide don’t do business accounts (they had some plans to do so, but they’ve now been scrapped 
).
And whilst Monzo score the same on the table, in the text of the most recent Ethical Consumer report in their magazine they point out that:
Monzo is almost 25% owned by Passion Capital – jointly owned by Stefan Glaenzer, who pled guitly of sexual assault in 2012. (Monzo’s other major investor is owned by the brother of Jared Kushner, senior advisor and son-in-law to Donald Trump.)
When Ethical Consumer asked the app banks about ethics, “only Starling appeared to have any kind of ethical policy for it’s lending services” who said:
“We do not privde banking services to organisations that use excessive power to systemically promote public behaviour that is harmful to individuals, groups or to the whole of society in order to maximise their own profits. They may include, for example, arms manufactures and tobacco companies… We lend to UK-based individuals and small businesses and, as policy, don’t lent to companies involved in extracting fossil fuels”.
Ethical Consumer therefore conclude that:
“If you particularly want to switch to an app-only bank, Starling appears marginally more engaged than the others on ethical issues”.
Re Revolut, Ethical Consumer point out that they are not covered by the Financial Services Compensation Scheme (FSCS) so the first £85,000 that is covered by Monzo, Starling and all the other banks is not covered with Revolut.
Apparently Revolut has also been accused of mistreating workers during the pandemic. According to Ethical Consumer:
“Revolut employees say they have been forced to choose between quitting their jobs voluntarily for a small severance payment or being fired”
So, imho the best option at present is Starling, so that’s who we’re going to switch to.