Some time ago I embedded Qlik in a web portal. I would recommend you to refer to the following Qlik Dev article where they would ask you to add the site to the admin console CSP and enable "frame-ancestors". If you do not do this, you will not be able to embed Qlik Sense Cloud in a web portal.
After the rules are applied, I would recommend waiting 5-10 minutes, then refresh the site and probably redirect you at Qlik login or IdP login.
How do you create custom content in this third party application? Do you own the source code, or is it surfacing up a simple web app that you'd embed Qlik into?
What web technologies are you familiar with/ prefer working with?
Which platforms will the app run on? Some platforms block third party cookies by default in some contexts, which means you can't use our current iframe solution
What do you want to embed - is it a whole sheet layout or are you willing to build a more embedded experience using one of our JS frameworks
What method of authentication does this web app use? You'll likely want to ensure that users don't have to sign into the app, and then into Qlik Cloud - thinking about auth up front will provide a better experience for your users- what is the mobile app written in, what technologies are