https://piunikaweb.com/2020/12/08/one-ui-3-0-removes-smart-view-support-for-chromecast-says-moderator/   Here is the answer. Thinking going back to Sony phone now.

Same issue with Galaxy Note 10. So bed :( 

Can you please help to fix Smart View on my Galaxy Note 10. It's not working with chromecast devices after the last system update. Chromecast devices are simply not visible anyone. It was working fine before Android  11 update. Please help.

Can you please help to fix Smart View on my Galaxy Note 10. It's not working with chromecast devices after the last system update. It was working fine before Android 11 update. Please help.

Chromecast devices are not visible in Smart View. Everything was perfect before system update.