Hi 3cL1p5e7,
as written in the other thread (Integrate Internet Identity within iFrame - #7 by frederikrothenberger) we definitely plan to give developers more control over the headers of their canisters HTTP responses (including the possibility to make pages embeddable within iFrames). We are just not there yet (as there are some security issues to solve).
I will update this thread once the feature is available.
Best regards,
Frederik