Dear Dharam,
Good day!!
I understand your concern and I have the tested the behavior at my end by adding the provided embedded code into the Embed webpart and adding the domain to the HTML Field Security in the SharePoint Online site settings:
After adding the domain successfully, I have refreshed my SharePoint Online site page where I am adding the Embed code and place the embed webpart, it works perfectly at my end:
As you have added the both domains successfully, please try to remove added Embed webpart in the page> Refresh the page> Edit the page> Add the Embed webpart> Add the code (Note: Please remove htmlCopy Code from your iFrame which place at the start)> After adding the code, please hover your mouse outside the embed code box and click anywhere.
If you are able to see the content, then please try the another embed code as well.
If it didn’t work, please create a new SharePoint Online page and see whether it works normally.
Sorry for the inconvenience caused and thanks for your patience.
Best Regards,
Sophia