I wrote my first tutorial today. It started out from trying to help @SamA74 in a Docker thread he started. I figured it would be good to write it out for my own future reference and ended up just doing a tutorial to share. Let me know what you think or if you find any problems with it or implementing the steps. Enjoy!
https://galaxyinternet.us/docker-lamp-stack-with-composer-psr-4-autoloading/