Which array processing programming language should I learn? (APL/J/K)

For years now, I want to learn one of the array processing programming languages, such as APL, J or K, and this pandemic is good excuse to do it, instead of netflixing.

Which one should I learn and why?

The main criteria I'm interested in are:

- intelectual/conceptual interest

- quality and quantity of current learning resources

- open-source

- ease of use/usefullness for power-users (I'm ok with a steep initial learning curve, if it pays out later)

Thanks!