I've been wanting to get around to learning an apl-like language like K for a while. Is there any favorite starting points for anyone who's done this?

check out oK[0] by John Earnest, who is the author of the content of this post.

it has a well-written manual and is a great jumping off point. the source is written in ~1000 lines of js. so you can look at how each primitive is implemented.

there is a k-enthusiast element.io server[1] where you can ask any question you like. folks are friendly!

EDIT: another commenter shared most of this info. oops :-) i'll add as well ngn-k browser repl[2] which has some docs and a fuller feature-set than oK. this is probably the most-used open source k right now. the author is active in the above element server, and still patches bugs and makes updates.

[0] https://github.com/JohnEarnest/ok

[1] https://matrix.to/#/#aplfarm-k:matrix.org

[2] https://ngn.codeberg.page/k/#