> Of course plenty of sites don't actually work with autofill, even the browser builtin autofill, because they don't mark the form fields properly.

Can't KeePass use the autotype functionality, but still filter it by website domain/host that it gets from the extension? So basically you'll still never have to copy&paste, and any site requiring this would be a reliable red flag?

Yes, that should generally work. I'm sure someone will decide to make a page requiring a CAPTCHA in between entering the username & the password to create an exception to this case though. It's the sort of insecure-by-design nonsense banks love.