Flux allows you to display external engagement tools on your website only to users who are particularly receptive to this type of engagement.
However, sometimes it makes more sense to link directly to an external website instead of an embed. For example, you could make a special offer to a segment of users who return to your site frequently.
Write as a prompt something like "Hello {fist name}, welcome back! Today only we have a special offer for you: 20% off". Then link to a corresponding special offer page in your subscription system.
You can also use this for other occasions, for example, to draw attention to the landing page of an event, or to sell products or promote a social media account.