Laravel/PHP package development

I've been pretty curious into learning more about package development for php so that I have composer installable packages.

After some initial research I came across Marcel Pociot's course and was curious if anyone had purchased it and enjoyed it. I would love some feedback on the course or other avenues I should look into to learn more about package development.

Relevant info: definitely aiming for laravel packages, but also would like to learn about framework agnostic package dev.