Use “name” query string to refer to form field instead of pagename

When handling form submissions, it would generally be advisable to POST your form to a custom AJAX handler or wp-admin/admin-post.php form handler. If an external API integration requires you to accept the name parameter, setting up this functionality as a REST API endpoint or controller would give you fairly complete control over the query vars.

That said, you can use the request filter to remap incoming querystring variables. In this case, I would recommend reassigning name‘s value to something else internally so as to not break anything else or require any other hacky work-arounds.

Most “pretty permalink” permastructs will map the URI /myslug to the pagename=myslug query var key/value. That in mind, we can re-assign name for your page as such:

function wpse391078_remap_myslug_page_name_var( $qvs ) {
  if( ! empty( $qvs['pagename'] ) && $qvs['pagename'] === 'myslug' ) {
    $qvs['wpse391078_name'] = $qvs['name'];
    unset( $qvs['name'] );
  }

  return $qvs;
}
add_filter( 'request', 'wpse391078_remap_myslug_page_name_var' );