Ask HN: Best upskilling courses for software engineers?

I'm looking around for courses to recommend to members of my teams to help grow their software engineering skills, and coming up... pretty short.

I've got a few books that have proven to be excellent -- Sandi Metz' are at the top of that list -- but not a lot of interactive courses, coaches, or teachers that I feel I could recommend.

I'll take recommendations for specific courses on Coursera and the like, but I'm particularly curious about small-group classes and/or coaching, where there's actual feedback and critique on the work being done.

Any pointers?