Report Designer tutorials - What are people's favorites? What gaps are there?

I’m thinking of developing some Report Designer content in my off time.

There’s a lot of stuff on the internet already, so I actually cover ground people want to know about/could do with a refresh I have a few questions for the community if anyone feels like sharing:

1. Existing content: What Videos/blogs/websites are your favorites for Report Designer tutorials?
2. Existing content: Are there any tutorials you REALLY recommend as amazing?
    
3. New content: What do you struggle to find information on?
4. New content: What information seems to be out of date?
5. New content: is there anything you just want a great tutorial out there for?

Sorry if this question gets asked a lot, I couldn’t see a recent post like this.