Some resources both 3rd & 1st party..

https://www.timestored.com/kdb-guides/

https://learninghub.kx.com/forums/forum/kdb/

https://dataintellect.com/thoughts/?_sft_category=blog

https://groups.google.com/g/personal-kdbplus?pli=1

https://k4.topicbox.com/groups/k4?subscription_form=e1ca20f8...

https://code.kx.com/q/kb/faq-listbox/