I’m currently developing a Teams App and came across this sample:

const appContentUrl = "https://www.bing.com/";

microsoftTeams.meeting.shareAppContentToStage((err, result) => {
    if (result) {
        // handle success
    }
    if (err) {
        // handle error
    }
}, appContentUrl);

Source: https://learn.microsoft.com/en-us/microsoftteams/platform/apps-in-teams-meetings/build-apps-for-teams-meeting-stage?tabs=desktop#example

When trying to show bing.com on meeting stage, I currently get the following error:
API is not supported in current context-Provided URL is invalid

Just for testing this, I’m allowing all domains on my manifest.

"validDomains": [
    "*"
],

Is it posible to show directly on meeting stage any URL (using microsoftTeams.meeting.shareAppContentToStage) or can I just show an URL between my Teams App?

This works just fine for me:

microsoftTeams.meeting.shareAppContentToStage((error) => {
    if (error) {
        // handle error
    }
}, `${window.location.origin}`);