If nobody objects, because I don’t find these things when I search for them, let me post here what I’ve learned. You can disable the “Connecting to …” banner that occurs when using SP-Initiated logins by adding the following to the afterRender event:
oktaSignIn.on('afterRender', function(context) {
var banner = document.getElementsByClassName("applogin-container");
if (banner.length) banner[0].style.display = "none";
}
});
Times change: the setting in the second post is now under customizations → branding → some brand, look on the settings tab. But it won’t turn off the header.
To complete the operation in the first post you have to set up a custom domain so that you can edit the sign-in page and wrap the JavaScript sign-in widget. This isn’t necessary, as soon as you edit the custom sign-in page, save it without any changes, and then publish, the banner and the footer will go away. They aren’t defined in the custom page, only on the default page.