My impression from my initial search were the courses were either very expensive or modeled for users for on the job training instead of job seekers (like myself) looking to upskill.
I "provisionally" passed the exam to be a certified WF Project Manager Professional today. All the info is in the public tutorials and documentation. Using the the criteria outline as a guide, it is doable. The practice exam on the criteria outline page does a good job of giving you an idea of the types of questions and the feel of the exam. Even though I passed, I wish I studied more on: Reporting steps, Status vs Conditions, and Agile settings. Overall I feel really confident that I can just start as a WF project owner and have a little badge to make potential employers more at ease. I watched some YouTube tutorials to get started, but the bulk of my studying was the Experience League tutorials/documentations and writing notes. With the outline, it's easier to track your progress and gives you a compass on what to study.
Hope that helps!