Integrating a custom Identity Proofing solution in Auth0


I have some questions regarding integrating a custom identity proofing solution with Auth0 (like the ones in the marketplace).

For what I have read and seen, I understand the only procedure to make an integration like this is to use Actions (since Rules are going to be deprecated)?
Is there other way (preferible an standard way, like OIDC)?

My objective is to make a custom action and later on propose an official marketplace integration.

I have read too about Rules (now discarded due to deprecation) and other integration solutions, but I don´t know how I may approximate my solution with these.

For more detail, its like a redirect/callback flow to an external page that handles identity proofing and then returns to Auth0.

Any kind of help and feedback is appreciated…
Thank you!