Adaptable Product Discovery is a well-documented framework developed and published by Tim Herbig. It provides even more guidance to the various phases of Product Discovery than the Double Diamond model.
This is the original title of the web site and the original is constantly being updated:
Product Discovery: A Practical Guide for Agile Teams (2021)
In a nutshell, Tim breaks down the complete Product Discovery into 6 phases:
Phases of Product Discovery
Just like Double Diamond, this framework also distinguishes between the problem space and solution space:
Contrary to what the initial hexagon suggests, Product Discovery is rarely a linear process. Rather, sometimes it is ok to cut corners. In other situations, it may be required to take a step back and start fresh because the team might got stuck: