Ask HN: Best Practices for Creating a Golden Record or Single Source of Truth?

Hey HN. I'm facing this challenge at my job where I receive user's data from N sources and need to create a single source of truth (a table with single entities for each user). I'm looking for best practices, I don't even know how to start it. When I look for that on the web I find many random "tutorials" where it ends up trying to sell you a tool for that purpose. If anyone could point me in a good direction/book/tutorial on that matter (Golden Record, SSOT, MDM, etc.) I would really appreciate it. Ps: I use GCP (BigQuery SQL) and Python. Thanks!