Not a fix but a situation that needs an explanation.
Mid 2010 MacBook running High Sierra lost Internal Speakers like a year ago. Only choices are headphones or Digital Output. Read every forum, tried every recommendation but nothing worked to restore them. I’ve been using headphones and/or Bluetooth speakers since.
Then one day I set up a dual boot system with Linux Ubuntu for the heck of it. When booted into Ubuntu the speakers started working. Boot into MacOS speakers stop working. I erased the entire disk and installed a fresh copy of High Sierra. Speakers won’t work.
Hopefully someone can take this info and help with a solution for all. Apple threw up their hands when I reported this.