add this to functions.php

/**

• Combined solution to force the Visual Editor in Opera Mobile
  */
  function ultimate_opera_mobile_gutenberg_fix() {
  $user_agent = $_SERVER['HTTP_USER_AGENT'] ?? '';

  // Check based on the specific User Agent provided
  if ( strpos($user_agent, 'OPR/') !== false && strpos($user_agent, 'Mobile') !== false ) {

   // 1. Server-side settings (PHP)
   $user_id = get_current_user_id();
   if ( $user_id ) {
       // Force the "Visual Editor" setting in user profile
       update_user_meta( $user_id, 'wp_rich_editing', 'true' );
   }
   
   // Force rich editing permission
   add_filter( 'user_can_richedit', '__return_true', 999 );
  
   // Disable script concatenation to improve loading compatibility
   if ( !defined('CONCATENATE_SCRIPTS') ) {
       define('CONCATENATE_SCRIPTS', false);
   }
  
   // 2. Inject Client-Side fix script (JS)
   add_action('admin_print_footer_scripts', function() {
       ?>
       <script type="text/javascript">
           (function() {
               function forceVisual() {
                   // Check if Gutenberg data stores are initialized
                   if (window.wp && wp.data && wp.data.dispatch('core/edit-post')) {
                       const mode = wp.data.select('core/edit-post').getEditorMode();
                       // If stuck in Code/Text mode, switch to Visual
                       if (mode === 'text') {
                           wp.data.dispatch('core/edit-post').switchEditorMode('visual');
                       }
                   }
               }
               // Run on initial load and again after a delay to ensure editor is ready
               window.addEventListener('load', forceVisual);
               setTimeout(forceVisual, 3000);
           })();
       </script>
       <?php
   }, 20);
  

  }
  }
  add_action( 'admin_init', 'ultimate_opera_mobile_gutenberg_fix' );

I’ve run into this with Opera before. In my case it was just the browser getting stuck. Clearing the cache and opening wp admin in a private window fixed it instantly. If that doesn’t work, try turning off Opera’s built in ad blocker because it can block some WordPress login scripts. Usually one of these three solves it.