Would it be possible to include a step in the sign up/onboarding flow that enables to pop up a modal that triggers to signup before people actually can use a service. When signup completed, the user should then be able to continue the actual action.
Do you mean a more dedicated onboarding flow where you can ask more questions before they can use the service? If so, we are actively building that (a flow / tool to better onboard your customers.)
That type of onboarding is flow is highly desired.
In this particular case, I am focusing more on the flow that an user start using the service but then gets a pop up that they need to sign up first before they can continue. If they sign up, then they can continue the flow as well, and the page is not refreshed.