Thomas Nield is a US software engineer and the author of Essential Math for Data Science (O'Reilly) — one of the most recommended modern introductions to the math foundations underneath data science work. He has previously been an O'Reilly author on Kotlin and reactive programming, and runs the Nield Consulting Group.
His CourseFlix listing carries Grokking Statistics — a structured treatment of the statistical foundations underneath data work: probability, distributions, hypothesis testing, regression, and the patterns that show up when reasoning about real-world data rather than textbook examples.
Material is paid and aimed at developers and analysts ready to fill the statistics-foundations gap. For broader content, see CourseFlix's Math & Statistics category page.