The Medium Method comes from the Todoist Productivity Articles, I haven't really seen it anywhere else by that name. It's quite simple.
Carry a pen and a notebook. Write notes. Capture tasks. Do general Bullet Journaling.
Do a Daily Review each night in which you look over your notes from the day and process any actions or ideas into a digital repository. Offload tasks from the page to a Task Manager. Capture deadlines or appointments into your calendar. Send Tweets about whatever jokes you thought of.
My Todoist Productivity Articles page has a GoodNotes 5 page on it. Can't really copy/paste that very well in Notion on the iPad.