UPDATE (25th Sepetember 2019): The Shenmue 3 demo is set to arrive "beginning this weekend" for backers of the trial tier of the game's Kickstarter, Ys Net has announced.
As announced previously, the demo offers a small taste of Shenmue 3 centered around "one day in Bailu Village near the beginning of the game". You can expect "story line elements, battling, minigames and more" - a little of everything, by the sounds of things.
There were some logistical details thrown in there too - keys received must be redeemed through the Epic Games Store, and you'll need 20GB of storage in order to play.