Kibana 7.4.0 embed=true not working as expected

I've just upgraded environment from 5.5.2 to 7.4.0, and everything is successful, except the dashboards that we're sharing embedded in an asp.net app via a reverse proxy appear not to be respecting the ?embed=true option. The dashboard works in the iframe, but the top bar and left 'menu' are still visible.

Sharing via Snapshot w/ ShortURL,if that makes a difference.

Any suggestions on what I'm missing in the new version?

Anyone have any suggestion here? Is this a known issue, or intentionally changed behavior, or something else, maybe?

I'm stuck at how to share the dashboard with business users safely and effectively.

Ping.

Same as your other post, it's being tracked as a bug here: Share snapshot - embed code not removing menus

Yes - I thought perhaps by using different words, I might get a different response.