Have you looked at the authParams.display option? It defaults to popup but can be changed to page. See this: https://github.com/okta/okta-signin-widget

From that github link:

authParams.display: Specify how to display the authentication UI for External Identity Providers. Defaults to popup

• popup: Opens a popup to the authorization server when an External Identity Provider button is clicked. responseMode will be set to okta_post_message and cannot be overridden.
• page: Redirect to the authorization server when an External Identity Provider button is clicked.

// Redirects to authorization server when the IDP button is clicked, and

// returns an access_token in the url hash (Implicit flow)

authParams: {

display: 'page',

responseType: 'token',

pkce: false

}