Any password manager should be able to “type in” the password. Or be a browser plugin that doesn’t rely on copy pasting, but use other mechanisms to inject it directly into the field.
But yes, if that’s their online portal, I am not kidding I would change banks.
I’ve used windows since the 90s. Not once have I intentionally used WordPad.
It did open by default for some file types for a long time (.doc), usually mangling the content cause it couldn’t actually handle them properly. I think it was also the default for .txt files at some point, causing many curse words when editing plain text files, that invisibly weren’t so plain any more after… Programs expecting a configuration fine really don’t like that sort of thing.
So: I’m very ok with this. Just install LibreOffice or something if you needa Word-like experience. Install notepad++ for anything “plain”.