List API: filters schema change

[ilyac-varicent]

Hello everyone,
First of all, thanks for doing great work supporting this tap.

I'd like to start publicly tracking or at least discuss the changes in how HubSpot is going to present list filters, e.g. contact_lists filters.
There's a couple of articles promising to deliver these changes on July 26, 2021:
[1] List API changes announcement
[2] New recursive filterBranch format description

Currently, the contact_lists.json schema defines a filters property.
But the API call /contacts/v1/lists now returns an empty array as a value of this property.
It returns a new property though: ilsFilterBranch which is a string containing seemingly valid JSON described by the article [2]

My questions:

1. Is there any ongoing activity around restoring v1 API behaviour?
2. What's your take on how Singer should address this issue?
3. How to define a recursive schema like this?

Thank you!