There's a Reddit that has a coding problem every day.
Which one?
https://www.reddit.com/r/dailyprogrammer/ - that's the one I know of. Sadly it's become defunct, but has a large number of problems going back over the years. I used to enjoy it as a kind of warmup at the start of my day.
A bit specialized but I like codegolf on stackexchange. Sure, the problem itself isn't the focus here, the implementation is, but it still does it for puzzling for me. I have finished all the regex crosswords I could find on the net...
This is a neat idea. If you're serious, I'd be willing to provide my email and chat through the idea and help out.
Why not. I am not sure if I would have both the level and the time though.