Check this asset with some examples of how to show a video in your iframe for all use cases.
https://www.outsystems.com/forge/component-overview/8606/web-embed-video-sample-react-application
ps: That asset on the forge is just a demonstration where you can have a look at how to do it.
"Sample application to demonstrate the implementation of playing (External/YouTube) video using IFrame and Video UI Control in the Reactive Web Application"
Regards,
Márcio