Beginning this week, Diablo 4 Twitch Drops will become available if you connect your Twitch and Battle.net accounts and tune in to any participating Twitch stream for up to six hours.
Official Diablo 4 Twitch Drops Blog How to Earn the Primal Instinct Mount
Starting today at 4 pm PST/7 pm EST, the first Week of Twitch Drops will become available to earn. This week is a double-whammy with both Rogue and Necromancer cosmetics becoming available.