With the deactivation of script tags API, the only way for merchants to show widget on legacy order status page is to insert code in to the “Order status page additional scripts” field in the Store Settings > Checkout page.
A merchant has notified me that this field is disabled for their store, and they are staying with legacy order status page as they have some other apps / requirement which they haven’t complete the migration yet.
Making this field disabled will render some apps that add widget to order status page useless for merchants who choose to stay on legacy order status page.
I hope Shopify can undo this action. Some merchants can’t even edit or remove existing code from the order status page script.
Thank you for the consideration.