How to effectively migrate from Hydrogen to Liquid?

[terciodejesus]

Hello everybody,

We are developing our store using Hydrogen. However, observing some advantages that Liquid has, let's start the migration process to use it in the conventional way using themes.

However, we have some pages that connect to external services via API (own applications) and we already have an entire functional structure both at the backend and frontend level, with many components.

What is the best way to take advantage of these pages that are already fully operational in Liquid?
One of the alternatives would be via IFRAME. Is it the best way? It's safe? What other alternatives?