After defeating Ultra Necrozma and returning to The Alola Region, the Ultra Recon Squad will continue to allow you to explore Ultra Space with the help of their Legendary Pokemon. While traveling through Ultra Space, you may sometimes enter a White Wormhole that leads to Ultra Jungle. This is the dwelling place of Buzzwole.
In order to battle Buzzwole, simply follow the vines upward to the tallest tree. After reaching the top, the nearby volcano will erupt and Buzzwole will appear. Buzzwole remains a Bug / Fighting Type Pokemon, always being found at Level 60 and knowing the moves of Counter, Hammer Arm, Lunge, and Dynamic Punch. Like all other Ultra Beasts, it can now be found in its Shiny Form. It will also respawn with each successive visit to this area.