The deck used to just be shared on reddit & such. But for all your questions, there is now a central "upstream" entity called AnkiHub that organizes and maintains updates to cards, syncs, etc. It's a $5/month subscription, but a lot of my friends just subscribe for a month each year to get the updates then unsubscribe.

All cards start suspended by default, and you unsuspend cards usually by tag. For example, lets say you watched a a popular third-party exam prep video from Boards & Beyond on Insulin. You would find the corresponding video has its own tag "tag:#AK\_Step1\_v12::#B&B::08\_Endocrinology::03\_Pancreas::03\_Insulin" which you would unsuspend all the cards for. That's the basic flow, but everyone does things a little differently.

Some people don't watch videos just do review questions from UWorld which are also tagged. Some people manage cards using a mix of tags and decks. Some people search and manually unsuspend cards individually. Some schools cross-tag cards with their lecture. Personally, I use an AI search to unsuspend cards by cross-referencing against a PDF of lecture for the day.

Custom tags can be protected when syncing from upstream: https://community.ankihub.net/t/protecting-fields-and-tags/1...