I once checked them out (or a provider they had bought, might be "Sofort") when all other options seemed worse.
IIRC I would have had to log into my bank account through them, giving them my login data and letting them read all of my transactions (data they use to gauge trustworthiness, I think). I was shocked that that's legal and amused to find out it probably isn't.
(Disclaimer: Highly anecdotal, it was multiple years ago)
