How can I track Hubspot iFrame form submissions in LinkedIn ads?

Question:
How can I track Hubspot iFrame form submissions in LinkedIn ads?

Product:
Wix Studio Editor

What are you trying to achieve:
I’m trying to set up conversion tracking for Linkedin ads for embedded Hubspot forms. How can I do this?

What have you already tried:
I have tried to implement conversion tracking via GTM, but that doesn’t work.