iFrame issue in Twenty Twenty-One (WordPress 5.6)

@himal64
I have removed your response to an old thread at https://wordpress.org/support/topic/iframe-issue-in-twenty-twenty-one-wordpress-5-6/?view=all#post-14690411

@marco-raaphorst I removed your bumps in this topic, and by that the topic got automatically closed for new replies (which happens after 6 months).
If you still have this problem, please make a new post, perhaps this time in the separate forum for your theme https://wordpress.org/support/theme/twentytwentyone/
When you do, also add information about how you add this embed: What editor are you using, which block type do you use, etc.