Thanks for posting in the community. If you would like the iframe to be responsive, you will need to add a custom CSS class or an id to the iframe. We're still working to expand our mobile functionalities, and unfortunately interactive hotspots are not yet supported in Lucidchart diagrams that are accessed from a mobile device.
If you'd like to see this feature considered for Lucidchart mobile in the future, please submit a Feature Request form. Our team uses this form to combine like requests and present them to our Product team.